Patent Publication Number: US-9424050-B2

Title: Parallelization and instrumentation in a producer graph oriented programming framework

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of application Ser. No. 11/607,196, filed Dec. 1, 2006, which is hereby incorporated by reference. 
    
    
     BACKGROUND 
     1. Field 
     Embodiments of the invention relate to the field of computers; and more specifically, to the field of programming and executing code with a runtime. 
     2. Background 
     Object-Oriented Programming 
     Object-oriented programming is a computer programming paradigm. The idea behind object-oriented programming is that a computer program may be seen as comprising a collection of individual units (called objects or instances) that act on each other, as opposed to a traditional view in which a program may be seen as a collection of functions, or simply as a list of instructions to the computer. An object is a language mechanism for binding data with methods that operate on that data. Each object is capable of being called through methods, processing data, and providing results to other objects. Each object can be viewed as an independent machine or actor with a distinct role or responsibility. 
     A reflective object-oriented language is a programming language that has a particular set of characteristics (e.g., classes, objects/instances, inheritance, reflection, etc.), whereas a reflective object-based language is sometimes used to label a programming language that has some subset of those characteristics (e.g., objects). For purposes of this document, the phrases “object-oriented source code” and “object-oriented code” will be used to refer to code written in a language that has such characteristics (e.g., code written in a reflective object-oriented language, code written in a reflective object-based language). While procedural languages, non-reflective object-oriented languages, and non-reflective object-based languages are programming languages that do not typically support such characteristics, transformation techniques may be used to provide such characteristics (e.g., through emulation) to code properly written in such languages; and thus, such techniques transform such languages into a reflective object-based language or reflective object-oriented language. (These techniques need not emulate all characteristics of object oriented or based languages, but may emulate only those characteristics which are of interest to the rest of this document) For purposes of this document, the phrases “object-oriented source code” and “object-oriented code” will also be used to refer to such transformed procedural, non-reflective object-oriented, and non-reflective object-based language code. By way of example, and not limitation, this document primarily describes object-oriented source code written in a reflective object-oriented language. Also, the terms object and instance are used interchangeably herein. 
     Used mainly in object-oriented programming, the term method refers to a piece of code that is exclusively associated either with a class (called class methods, static methods, or factory methods) or with an object (called instance methods). Like a procedure in procedural programming languages, a method usually consists of a sequence of statements to perform an action, a set of input parameters to parameterize those actions, and possibly an output value of some kind that is returned. 
     When programmers write a program using an object-oriented language, the resulting code can be conceptually viewed as including four basic types of code. The first type includes commands that operate on input instance(s) to provide output instance(s) (referred to herein as “transformation” code); typically written as methods (referred to herein as “transformation” methods). The second type includes instance instantiation commands that cause the runtime to instantiate instances of classes (referred to herein as “instance instantiation” code). The third type includes property manipulation commands (referred to herein as “data preparation” code) to invoke property methods (accessors, mutators, etc.) of the above instances. The fourth type includes sequences of commands that cause method invocation sequencing using the appropriate instances (where the appropriate instances include the instances to use as arguments, the instances to be used by instance methods, and the meta class instances used by class methods) to specify what transformation methods of what instances to invoke, in which order, and with which parameters of which instances responsive to the changes made by data preparation code (referred to herein as “manual invocation sequencing” code). The manual invocation sequencing code is sometimes written as methods separate from the transformation methods, and thus the manual invocation sequencing code includes sequences of invocation commands for the transformation methods. A program typically iterates between data preparation code and manual invocation sequencing code (which may also dip into the instance instantiation code), which in turn invokes transformation code (which may also dip into the instance instantiation code and data preparation code types). It should be noted that this is a conceptual representation of a program, and thus, should not be taken as an absolute with regard to how to view a program. 
     Runtime 
     The term runtime is used herein to refer to a program or library of basic code that runs other code written in the same and/or a different language. Thus, a runtime is a collection of utility functions that support a program while it is running, including working with the operating system to provide facilities such as mathematical functions, input and output. These make it unnecessary for programmers to continually rewrite basic capabilities specified in a programming language or provided by an operating system. Since the demarcation between a runtime and an operating system can be blurred, the term runtime is used herein to refer to code separate from the operating system and/or code that is part of the operating system. 
     Early runtimes, such as that of FORTRAN, provide such features as mathematical operations. Other languages add more sophisticated features—e.g., memory garbage collection, often in association with support for objects. More recent languages tend to have considerably larger runtimes with considerably more functionality. Many object-oriented languages also include a system known as the “dispatcher” and “class loader.” The Java Virtual Machine (JVM) is an example of such a runtime: it also interprets or compiles the portable binary Java programs (byte-code) at run time. The common language runtime (CLR) framework is another example of a runtime. 
     Programming and Execution Framework 
     One framework within which applications are provided to end users includes three basic divisions. The first division includes the creation of the operating system and runtime. This first division is performed by programmers with highly advanced programming skills. When working in this division, programmers are respectively referred to as operating system programmers and runtime programmers. When creating a runtime for an object-oriented language, the runtime programmers include support for executing the various types of commands used in transformation code, instance instantiation code, data preparation code, and manual invocation sequencing code (e.g., instance instantiation commands, data preparation commands, and method invocation commands). 
     The second division includes the creation of object-oriented application source code to be run by the runtime. The second division is again performed by programmers with highly advanced programming skills, as well as an understanding of the business objectives of the application. When working in this division, programmers are referred to as application programmers. When creating an application in an object-oriented programming language, the application programmers write the specific transformation code, instance instantiation code, data preparation code, and manual invocation sequencing code for the specific application being created. As part of this, if the application requires a graphical user interface, the application programmers also design and code the graphical user interface for the specific application; and thus are also referred to as application designers. 
     The third division includes the use of application programs being run by the runtime. The third division is performed by end users that need not have any programming skills. 
     Manual Invocation Sequencing Code 
     The greatest costs typically associated with the creation of an application involve the debugging and/or optimization of the manual invocation sequencing code. For each opportunity for data to change, the application programmer must consider its effect and write manual invocation sequencing code to cause the appropriate transformation methods of the appropriate instances to be invoked in the appropriate order with the appropriate inputs. Exemplary mistakes made by application programmers include: 1) invoking the appropriate transformation methods of the appropriate instances in the wrong order; 2) forgetting to include commands to cause the one or more required transformation methods of instances to be invoked responsive to some data being changed; 3) including commands to cause unnecessary transformation methods of instances to be invoked responsive to some data being changed (e.g., including commands to invoke transformation methods of instances that are not affected by the change in data), etc. 
     By way of example, one technique of generating manual invocation sequencing code is the use of the observer pattern (sometimes known as “publish subscribe”) to observe the state of an instance in a program. In the observer pattern, one or more instances (called observers or listeners) are registered (or register themselves) to observe an event which may be raised by the observed object (the subject). The observed instance, which may raise an event, generally maintains a collection of the registered observers. When the event is raised, each observer receives a callback from the observed instance (the observed instance invokes a “notify” method in the registered observers). The notify function may pass some parameters (generally information about the event that is occurring) which can be used by the observers. Each observer implements the notify function, and as a consequence defines its own behavior when the notification occurs. 
     The observed instance typically has a register method for adding a new observer and an unregister method for removing an observer from the list of instances to be notified when the event is raised. Further, the observed instance may also have methods for temporarily disabling and then reenabling calls to prevent inefficient cascading of a number of related updates. Specifically, callbacks called in response to a property value change often also change values of some other properties, triggering additional callbacks, and so on. 
     When using the observer pattern technique, application programmers writing manual invocation sequencing code specify what methods of what instances to call, in which order, and with which inputs by registering, unregistering, disabling, and reenabling observers to different observed instances, as well as writing the notify and callback methods for each. More specifically, the relationship between observer and observed instances is locally managed (by the observed instance alone, without synchronization with other observed instances) within the observer pattern, and thus the manual invocation sequencing code needed to synchronize events from multiple observed instances is typically part of the specific callback methods of each observer. 
     Overwriting, Volatile Call Stack 
     Typical runtimes use an overwriting, volatile call stack to track currently invoked, uncompleted calls. An overwriting, volatile call stack is overwriting in that it pops off and discards entries as each call is completed, and volatile in that it is discarded and rebuilt on every execution. Typical runtimes use overwriting, volatile call stacks because typical runtimes combine the building of the overwriting, volatile call stack with the actual invocation of the appropriate transformation methods of the appropriate instances with the appropriate inputs responsive to execution of the manual invocation sequencing code. In sum, responsive to execution of manual invocation sequencing code, a typical runtime determines the transformation method of instance sequencing call by call (as each call is made) and maintains the overwriting, volatile call stack to track only currently invoked, uncompleted calls. 
     Program Execution and Parallelization 
     Conventionally, methods in a program are executed sequentially based on the manual invocation sequencing code. To improve the efficiency and speed of execution, some methods may be executed in parallel in systems that support parallelization. In general, parallelization in computing is the execution of multiple processes, tasks, or threads, simultaneously. To implement parallelization, application programmers may identify methods that are desired to be executed in parallel, and then rewrite the manual invocation sequencing code to cause the methods identified to be executed in parallel. 
     Currently, common parallelization mechanisms supported in computing include multiprocessing and multithreading. In multiprocessing, an application program is typically divided into multiple tasks. Each task is a logically high level, discrete, independent section of computational work executable by a processor. To achieve parallization, at least some of the tasks are executed on multiple processors simultaneously. The processors may be coupled to each other via a network and be collectively referred to as a grid. The processors in the grid may include local processors, distant processors, or a combination of both. 
     Besides multiprocessing, another common parallelization mechanism is multithreading. A thread is a local process to execute a task. A processor that supports multithreading may execute multiple threads substantially in simultaneously. One example of such a processor is a multi-core processor, where each core of the multi-core processor may execute a thread. 
     By way of example, one conventional technique in parallelization is to analyze the source code of an application program to extract a configuration of the application program. Based on the configuration, the application program is divided into a number of sub-programs, which are presented in a graph based on the sub-programs&#39; parent-child relationships. These sub-programs are executed in parallel based on the sub-programs&#39; parent-child relationships. 
     In some conventional computing system, analysis of the intermediate code generated from the source code may be performed to achieve parallelization. For example, analysis of intermediate code (e.g., assembly language) and parallelization is done during compilation. A parallelizer of the compiler converts the intermediate code into a parallelly executable form. An execution order determiner determines the order of the basic blocks to be executed. An expanded basic building block parallelizer subdivides the basic building blocks into execution units, each made up of parallelly executable instructions. Analysis of dependency is done on an instruction basis. 
     However, the conventional techniques described above all require analysis of the manual invocation sequencing code in the application program, which is written by application programmers. Thus, the burden of parallelization is put onto the application programmers because great care has to be taken when writing the manual invocation sequencing code in order for the parallelization to be performed correctly. Thus, the application programmers need to possess a relatively high level of programming skill. 
     To make the job of application programmers easier, some conventional techniques have been developed to perform parallelization of application programs without requiring high level of programming skill. For example, special language constructs and special wrapper classes around regular data types are provided to execute a sequential program in parallel. Programmers are not required to write a “parallel program” in order to have parallel execution of parts of the program. A parallel procedure is specified at calling point by specifying a parallel procedure identifier and its arguments to the system. Execute parallel function to execute different parts in parallel is provided. Parallel procedures may be written by making a new class derived from a common class corresponding to each parallel procedure in the program. The system resolves dependencies at run time and parallelization is done to the level where actual dependency is encountered. The compiler may determine whether arguments can be modified in the parallel procedure through analysis of the control flow graph of the parallel procedure. 
     In another conventional computing system, a database manager is used in executing user-defined functions in an application program without the need of hard-coding all the parallelism support in the computer program itself. A database table is defined with instructions the user wants to execute in parallel. A user-defined function is then defined that executes the instructions in the table. The database manager provides parallelism by executing multiple tasks in parallel in the user-defined function. 
     Software Instrumentation 
     In general, software instrumentation refers to techniques for observing the behavior of one or more application programs and collecting metrics relevant to the application programs and the execution thereof. Thus, software instrumentation is a valuable tool in development as well as maintenance of an application program as the application program and/or the execution of the application program may be improved in various ways based on the behavior of the application program and the metrics collected. 
     Currently, various techniques have been developed to implement software instrumentation. For example, one technique is to add software modules or code to record the execution history of an application program such that future execution of the application program may be managed based on the execution history recorded. In another example, a compiler generates instruction and metadata for monitoring and collecting metrics. If a selected indicator is associated with an instruction, counting of events associated with the execution of the instruction is enabled. Then the number of times an instruction is executed is counted. After execution of the application program, hotspots are identified to determine performance improvement methodology and source code of the application program may be modified accordingly to implement performance improvement methodology. 
     Another conventional technique in instrumentation is to use the intermediate representation (IR) data generated from the source code of an application program. Specifically, a compiler generates IR data from source code. A code instrumentation module acts on the IR data to construct an IR tree and to add instrumentation to the IR data based on the IR tree. Then the compiler finishes compilation by converting the IR data with instrumentation into object code. A class instance can be instrumented using an instrumentation library (hereinafter, an instrumentation DLL). A virtual machine (VM) runtime module may run the instrumented class instance. There are declarations of method names and parameters in the byte code in the class instance. A special designator indicates that the executable portions correspond to the declared methods are found in some blocks of native code separate from the VM runtime module. For example, the instrumented Java VM byte code may be monitored during execution by a monitor process and a monitor library (a.k.a. a monitor DLL). 
     Object-Relational Mapping 
     Object-Relational mapping is a programming technique that links relational databases to object-oriented language concepts, creating (in effect) a “virtual object database.” Some object-relational mappers automatically keep the loaded instances in memory in constant synchronization with the database. Specifically, after construction of an object-to-SQL mapping query, first returned data is copied into the fields of the instances in question, like any object-SQL mapping package. Once there, the instance has to watch to see if these values change, and then carefully reverse the process to write the data back out to the database. 
     Hibernate 3.0 is an object-relational mapping solution for Java and CLR (Jboss® Inc. of Atlanta, Ga.). Thus, Hibernate provides a framework for mapping an object-oriented domain model to a traditional relational database. Its goal is to relieve the developer from some common data persistence-related programming tasks. Hibernate takes care of the mapping from classes to database tables (and from object-oriented data types to SQL data types), as well as providing data query and retrieval facilities. Hibernate is instance centric and builds graphs representing relationships between instances. 
     Inversion of Control and the Dependency Inversion Principle 
     Inversion of Control, also known as IOC, is an object-oriented programming principle that can be used to reduce coupling (the degree to which each program module relies on each other module) inherent in computer programs. IOC is also known as the Dependency Inversion Principle. In IOC, a class  X  depends on class  Y  if any of the following applies: 1)  X  has a  Y  and calls it; 2)  X  is a  Y ; or 3)  X  depends on some class  Z  that depends on  Y  (transitivity). It is worth noting that  X  depends on  Y  does not imply  Y  depends on  X ; if both happen to be true, it is called a cyclic dependency:  X  can&#39;t then be used without  Y , and vice versa. 
     In practice, if an object  X  (of class  X ) calls methods of an object  y  (of class  Y ), then class  X  depends on  Y . The dependency is inverted by introducing a third class, namely an interface class  I  that must contain all methods that  x  might call on  y . Furthermore,  Y  must be changed such that it implements interface  I .  X  and  Y  are now both dependent on interface  I  and class  X  no longer depends on class  Y  (presuming that  X  does not instantiate  Y ). This elimination of the dependency of class  X  on  Y  by introducing an interface  I  is said to be an inversion of control (or a dependency inversion). It must be noted that  Y  might depend on other classes. Before the transformation had been applied,  X  depended on  Y  and thus  X  depended indirectly on all classes that  Y  depends on. By applying inversion of control, all those indirect dependencies have been broken up as well. The newly introduced interface  I  depends on nothing. 
     The Spring Framework is an open source application framework for the Java platform that uses IOC and dependency inversion. Specifically, central in the Spring Framework is its Inversion of Control container that provides a means of configuring and managing Java objects. This container is also known as BeanFactory, ApplicationContext or Core container. Examples of the operations of this container are: creating objects, configuring objects, calling initialization methods and passing objects to registered callback objects. Objects that are created by the container are also called Managed Objects or Beans. Typically the container is configured by loading XML files that contain Bean definitions. These provide all information that is required to create objects. Once objects are created and configured without raising error conditions they become available for usage. Objects can be obtained by means of Dependency lookup or Dependency injection. Dependency lookup is a pattern where a caller asks the container object for an object with a specific name or of a specific type. Dependency injection is a pattern where the container passes objects by name to other objects, either via constructors, properties or factory methods. Thus, the Spring Framework is memory centric and builds graphs representing relationships between instances. 
     Graphing Tools 
     Javadoc™ is a tool that parses the declarations and documentation comments in a set of Java source files and produces a corresponding set of HTML pages describing (by default) the public and protected classes, nested classes (but not anonymous inner classes), interfaces, constructors, methods, and fields (Sun Microsystems®, Inc. of Santa Clara, Calif.). Javadoc can be used to generate the API (Application Programming Interface) documentation or the implementation documentation for a set of source files. Javadoc is class and method centric and builds graphs representing the relationships between the combination of classes and their methods. 
     Another system for designing software applications includes graphs of objects analyzed by an interpreter to represent and reproduce a computer application. This system utilizes prewritten programming classes stored in code libraries, which can be written to follow the design patterns described in “Design Patterns” by Gamma et al, Addison Wesley 1995, “Patterns in Java” by Grand, Wiley Computer Publishing 1998, and/or high level Computer Aided Software Engineering (CASE) tools. More specifically, some such classes are based on the Observer behavioral pattern. The prewritten code libraries represent application state nodes, processing logic, and data flow of the system between various application states (i.e., the pre-written data elements of the application), so that a user need not write, edit, or compile code when creating a software application. Instead, a user manually edits a software application in a Graphical User Interface by editing visual objects associated with a current application state node, such as data within the application state node or processes performed within the application state node. Then, based on the changes made by the user to the current application state node, the interpreter displays the updated application state to the user for the application state which has just been edited. The system may then transition along a user-defined transitional edge to another application state where the user may optionally edit the next application state or the transitional edge. Changes to a graph may be made to instances of the graph which are implemented by the interpreter while the software application is running 
     This system for designing software applications may include visual representations of a running software application that can be made “usable” with an application controller. When a user changes visual objects, representing the running software application, the controller uses the input to induce the interpreter to make the change to the graph. The controller then waits for more changes. Further, visual representations of such software applications may be imported or exported as XML documents that describe the visual representation of the application, and thereby the software application. 
     In order to edit and/or create a software application, in the form of a visual representation of nodes, directed edges, and application states, an application program interface and an application editor may further be included in the system. Key words, and associated definitions, from the pre-written code libraries, enable application developers to manually define a software application, processing steps, as well as the visual representation of a software application by providing graphical representations, within an editor, of a graph application which closely correlates to the actual application structure. A user defines a new application through an “application definition wizard,” which after certain preliminary matters are fulfilled, displays the new application as a graph component within the editor workspace. A user further interacts with an application by making selections from displayed lists of pre-created possible application components and dragging and dropping components onto the workspace using a PC&#39;s mouse and keyboard. A user may select components and “drag” them over existing components. When a new component is “dropped” on an existing component, the new component becomes a child of the existing component within an application graph. The relationships of components within the application are manually defined by the user&#39;s selections within the editor. Thus a tree structure representing an application is built by the user. As the application is created, a user can select an application navigator viewer to display a tree view of the constructed application making it possible to select and edit any component of the application. The editor interface processes user inputs and selections including creating or deleting application elements, updating component attributes, and updating display properties of an application. 
     The system described above, while utilizing visual representations of software applications, may also be used as a visual programming tool for defining and updating relational databases. The system utilizes XML descriptions of visual representation of software applications. A tool parses and interprets the XML descriptions to produces equivalent relational database table schemas, as well as changes thereto. When data is changed within a visual representation of a software application, a description of the change is stored along with other changes in a journal file and then processed as a group. An intermediate program (a java application operating on its own thread) performs transactions between the visual representation of the software application and the relational database. The java application polls (i.e., checks) the journal of changes to nodes of the visual representation (i.e., data in database), and if there are changes, makes the changes to the database. Thus, by altering data within the visual representation, the system updates a database. A similar application stands between the visual representation of the software application and the database to handles requests for data from the database. 
     Another system for analyzing software is called a Code Tree Analyzer (CTA). A CTA analyzes static source code written in an object-oriented programming language. The CTA generates a symbol table and a call tree from the static source code. Using the symbol table, the CTA generates a class diagram. Likewise, using the call tree, the CTA generates a sequence diagram. The class diagram illustrates the relationship between a user selected class and classes related to the user selected class. The sequence diagram illustrates the sequence in which different methods are called. Using both the class diagram and the sequence diagram, the CTA generates a design artifact representative of the static source code. When the user modifies the design artifact, the CTA identifies impacted portions of the source code using the sequence diagram. The design artifact is used for code maintenance and/or reverse engineering of the static source code. 
     U.S. Pat. No. 5,966,072 describes use of a graph to invoke computations directly. Getting information into and out of individual processes represented on the graph, moving information between the processes, and defining a running order for the processes, are discussed. The described arrangement adds “adaptor processes”, if necessary, to assist in getting information into and out of processes. 
     BRIEF SUMMARY 
     Embodiments of parallelization and/or instrumentation in a producer graph oriented programming framework have been presented. In one embodiment, a request to run an application program is received, wherein object-oriented source code of the application program includes methods and producer dependency declarations, wherein the producer dependency declaration for a given method identifies a set of zero or more producers with outputs that are an input to the given method, wherein a producer is at least an instance and a method associated with that instance. Further, execution of the application program may be parallelized based on dependency between producers of the application program using the runtime. In some embodiments, the application program is instrumented using the runtime. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may best be understood by referring to the following description and accompanying drawings that are used to illustrate embodiments of the invention. In the drawings: 
         FIG. 1A  is a block diagram illustrating the relationship of a producer dependency declaration for a method of a class in object oriented-source code to an instance of a producer based on that method from a given instance, according to one embodiment of the invention; 
         FIG. 1B  illustrates exemplary relationships between the producer  110 A and the parent producer  114 A. 1  according to one embodiment of the invention; 
         FIG. 1C  illustrates exemplary relationships between the producer  110 A and the child producer  112 A. 1  according to one embodiment of the invention; 
         FIG. 1D  illustrates some additional exemplary combinations of relationships of parent producers  114  and child producers  112  to producer  110 A according to one embodiment of the invention; 
         FIG. 1E  illustrates that different instances of the same class can have producers based on the same and/or different methods according to one embodiment of the invention; 
         FIG. 2  is a block diagram illustrating the reusability of a runtime with producer graph oriented programming support according to one embodiment of the invention; 
         FIG. 3A  is a block diagram illustrating a runtime with producer graph oriented programming support according to one embodiment of the invention; 
         FIG. 3B  is a block diagram illustrating a runtime with producer graph oriented programming support that also supports incremental execution and overridden producer outputs according to one embodiment of the invention; 
         FIG. 4A  is a block diagram illustrating the discovery and building of an exemplary producer graph according to one embodiment of the invention; 
         FIG. 4B  is a block diagram illustrating the initial execution of the producer graph of  FIG. 4A  according to one embodiment of the invention; 
         FIG. 4C  is a block diagram illustrating the incremental execution of the producer graph of  FIG. 4B  according to one embodiment of the invention; 
         FIG. 4D  is a block diagram illustrating the incremental execution of the producer graph of  FIG. 4B  after dependent producer  2  has been overridden according to one embodiment of the invention; 
         FIG. 4E  is a block diagram illustrating the incremental execution of the producer graph of  FIG. 4B  after dependent producer  2  has been overridden and independent source producer  3  has been modified according to one embodiment of the invention; 
         FIG. 5A  is a block diagram illustrating the discovery and building of an exemplary producer graph including an unresolved dependency according to one embodiment of the invention; 
         FIG. 5B  is a block diagram illustrating the initial execution of the producer graph of  FIG. 5A  and the resolution of the unresolved dependency according to one embodiment of the invention; 
         FIG. 5C  is a block diagram illustrating the initial execution of the producer graph of  FIG. 5A  and/or the reexecution of the producer graph of  FIG. 5B  according to one embodiment of the invention; 
         FIG. 5D  is a block diagram illustrating the initial execution of the producer graph of  FIG. 5A  and/or the reexecution of the producer graph of  FIG. 5B or 5C  according to one embodiment of the invention; 
         FIG. 6  is a flow diagram a logical execution flow of a runtime client and its relationship to a runtime with producer graph oriented programming support according to one embodiment of the invention; 
         FIG. 7A  illustrates pseudo code of a producer dependency declaration for a method using shortcut dependencies according to one embodiment of the invention; 
         FIG. 7B  is a block diagram of exemplary producers according to one embodiment of the invention; 
         FIG. 7C  illustrates pseudo code of a producer dependency declaration for a method using a non-shortcut dependency, and illustrates a block diagram of exemplary producers according to one embodiment of the invention; 
         FIG. 7D  illustrates pseudo code of a producer dependency declaration for a method using a non-shortcut dependency according to one embodiment of the invention; 
         FIG. 7E  is a block diagram of exemplary producers according to one embodiment of the invention; 
         FIG. 7F  is a block diagram of an exemplary dependencies through use of a UpwardDependency with a dependency determination producer according to one embodiment of the invention; 
         FIG. 7G  is a block diagram of possible exemplary dependencies through use of a WeaklyConstrainedDependency with a dependency determination producer according to one embodiment of the invention; 
         FIG. 7H  illustrates exemplary producer graphs of standard producers according to one embodiment of the invention; 
         FIG. 7I  illustrates one example of producer dependencies and dependency determination producers for discovering, resolving, and building the producer graph of  FIG. 7H ; 
         FIG. 8A  is a block diagram illustrating a first exemplary framework within which applications are provided to end users according to one embodiment of the invention; 
         FIG. 8B  is a block diagram illustrating a second exemplary framework within which applications are provided to end users according to one embodiment of the invention; 
         FIG. 8C  illustrates an exemplary screenshot and usage of free cell selection with the configurable interactive producer output layout graphical user interface module  840  according to one embodiment of the invention; 
         FIG. 8D  illustrates another exemplary screenshot and usage of free cell selection with the configurable interactive producer output layout graphical user interface module  840  according to one embodiment of the invention; 
         FIG. 8E  illustrates an exemplary screenshot and usage of table creation with the configurable interactive producer output layout graphical user interface module  840  according to one embodiment of the invention; 
         FIG. 8F  illustrates another exemplary screenshot and usage of table creation with the configurable interactive producer output layout graphical user interface module  840  according to one embodiment of the invention; 
         FIG. 9A  is a block diagram illustrating a first scheme for distributing a runtime with producer graph oriented programming support according to one embodiment of the invention; 
         FIG. 9B  is a block diagram illustrating a second scheme for distributing a runtime with producer graph oriented programming support according to one embodiment of the invention; 
         FIG. 9C  is a block diagram illustrating a third scheme for distributing a runtime with producer graph oriented programming support according to one embodiment of the invention; 
         FIG. 10  is a block diagram of an exemplary implementation according to one embodiment of the invention; 
         FIG. 11A  is a block diagram of an example of the class tracking structure  1092  of  FIG. 10  according to one embodiment of the invention; 
         FIG. 11B  is a block diagram of an example of the instance tracking structure  1065  of  FIG. 10  according to one embodiment of the invention; 
         FIG. 11C  is a block diagram of an example of the producer graph(s) structure  1060  of  FIG. 10  according to one embodiment of the invention; 
         FIG. 11D  is a block diagram of an example of the method tracking structure  1058  of  FIG. 10  according to one embodiment of the invention; 
         FIG. 11E  is a block diagram of an example of a serialized form local map used in multiprocessing according to one embodiment of the invention; 
         FIG. 11F  is a block diagram of an example of a runtime setting structure  1048  of  FIG. 10  according to one embodiment of the invention; 
         FIG. 11G  is a block diagram of an example of a producer-based configurable decision structure  1049  of  FIG. 10  according to one embodiment of the invention; 
         FIG. 12A  is a block diagram illustrating additional detail of  FIG. 10  to support multiprocessing according to one embodiment of the invention; 
         FIG. 12B  is a block diagram illustrating additional detail of  FIG. 10  to support contingent and subscription type dynamic producer dependencies according to one embodiment of the invention; 
         FIG. 13A  illustrates pseudo code of producer dependency declarations for methods using a non-shortcut, non-dynamic (non-contingent, non-subscription) dependency according to one embodiment of the invention; 
         FIG. 13B  is a block diagram of producers illustrating an exemplary non-shortcut, non-dynamic (non-contingent, non-subscription) producer dependency according to one embodiment of the invention; 
         FIG. 13C  illustrates pseudo code of producer dependency declarations for methods using a non-shortcut, contingent, non-subscription producer dependency according to one embodiment of the invention; 
         FIG. 13D  is a block diagram of producers illustrating an exemplary non-shortcut, contingent, non-subscription producer dependency according to one embodiment of the invention; 
         FIG. 13E  illustrates pseudo code of producer dependency declarations for methods using both a non-shortcut, contingent, non-subscription producer dependency and a shortcut, contingent, non-subscription producer dependency according to one embodiment of the invention; 
         FIG. 13F  is a block diagram of producers illustrating a non-shortcut, contingent, non-subscription producer dependency and a shortcut, contingent, non-subscription producer dependency according to one embodiment of the invention; 
         FIG. 13G  illustrates pseudo code of producer dependency declarations for methods using a shortcut, contingent, non-subscription producer dependency and a shortcut, non-contingent, non-subscription producer dependency according to one embodiment of the invention; 
         FIG. 13H  is a block diagram of producers illustrating an exemplary shortcut, contingent, non-subscription producer dependency and a shortcut, non-contingent, non-subscription producer dependency according to one embodiment of the invention; 
         FIG. 13I  illustrates pseudo code of producer dependency declarations for methods using a shortcut, non-dynamic (non-contingent, non-subscription) producer dependency according to one embodiment of the invention; 
         FIG. 13J  is a block diagram of producers illustrating an exemplary shortcut, non-dynamic producer dependency according to one embodiment of the invention; 
         FIG. 14A  is a block diagram of an example of the subscription log 1250 of  FIG. 12B  according to one embodiment of the invention; 
         FIG. 14B  is a block diagram of exemplary producers illustrating a non-contingent, absorbing subscription producer dependency according to one embodiment of the invention; 
         FIG. 14C  is a block diagram of exemplary producers illustrating a non-contingent, sticky subscription producer dependency according to one embodiment of the invention; 
         FIG. 14D  illustrates the choice of a parent producer based upon a parent dependency determination producer created by a sticky subscription according to one embodiment of the invention; 
         FIG. 14E  illustrates the choice of a parent producer based upon a parent dependency determination producer created by a child dependency determination producer, which child dependency determination producer is linked by a sequencing dependency, according to one embodiment of the invention; 
         FIG. 15  is a flow diagram for instantiating new instances according to one embodiment of the invention; 
         FIG. 16A  is a flow diagram for instantiating new producers and unoverriding producers according to one embodiment of the invention; 
         FIG. 16B  is a flow diagram for block  1623  of  FIG. 16A  according to one embodiment of the invention; 
         FIG. 17  is a flow diagram for block  1650  of  FIG. 16A  according to one embodiment of the invention; 
         FIG. 18  is a flow diagram for block  1745  of  FIG. 17  according to one embodiment of the invention; 
         FIG. 19  is a flow diagram for block  1630  of  FIG. 16A  according to one embodiment of the invention; 
         FIG. 20  is a flow diagram for blocks  1635  and  1670  of  FIG. 16A  according to one embodiment of the invention; 
         FIG. 21A  is a flow diagram for overriding producers according to one embodiment of the invention; 
         FIG. 21B  is a flow diagram for overriding producer execution mode settings according to one embodiment of the invention; 
         FIG. 21C  is a flow diagram for overriding execution mode settings globally at runtime level according to one embodiment of the invention; 
         FIG. 21D  is a flow diagram for overriding execution mode settings based on the producer-based configurable decision structure according to one embodiment of the invention; 
         FIG. 22A  is a part of a flow diagram for execution of the current producer graph(s) according to one embodiment of the invention; 
         FIG. 22B  is another part of a flow diagram for execution of the current producer graph(s) according to one embodiment of the invention; 
         FIG. 23  is a flow diagram for block  2205  of  FIG. 22A  according to one embodiment of the invention; 
         FIG. 24  is a flow diagram for block  2260  of  FIG. 22B  according to one embodiment of the invention; 
         FIG. 25  is a part of a flow diagram for execution of a set of ready producers substantially in parallel according to one embodiment of the invention; 
         FIG. 26  is another part of the flow diagram for execution of a set of ready producers substantially in parallel according to one embodiment of the invention; 
         FIG. 27A  is a part of a flow diagram for instantiating data structures before executing the set of ready producers according to one embodiment of the invention; 
         FIG. 27B  is another part of the flow diagram for instantiating data structures before executing the set of ready producers according to one embodiment of the invention; 
         FIG. 28A  is a flow diagram for executing producers using multithreading according to one embodiment of the invention; 
         FIG. 28B  is a flow diagram illustrating execution of a thread in multithreading according to one embodiment of the invention; 
         FIG. 28C  is a flow diagram for handling thread termination callback according to one embodiment of the invention; 
         FIG. 29A  is a part of a flow diagram for executing producers using multiprocessing and local execution according to one embodiment of the invention; 
         FIG. 29B  is another part of the flow diagram for executing producers using multiprocessing and local execution according to one embodiment of the invention; 
         FIG. 30  is a flow diagram for serializing inputs and/or an underlying instance of a producer to be multiprocessed according to one embodiment of the invention; 
         FIG. 31A  is part of a flow diagram for distant computing according to one embodiment of the invention; 
         FIG. 31B  is another part of the flow diagram for distant computing according to one embodiment of the invention; and 
         FIG. 32  is a flow diagram for local execution of producers according to one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous specific details such as logic implementations, opcodes, means to specify operands, resource partitioning/sharing/duplication implementations, types and interrelationships of system components, and logic partitioning/integration choices are set forth in order to provide a more thorough understanding of the invention. It will be appreciated, however, by one skilled in the art that the invention may be practiced without such specific details. In other instances, control structures, data structures, and full software instruction sequences have not been shown in detail in order not to obscure the invention. Those of ordinary skill in the art, with the included descriptions, will be able to implement appropriate functionality without undue experimentation. 
     Unless otherwise specified, dashed lines in the figures (with the exception of dashed dividing lines) are used to represent optional items in the figures. However, it should not be presumed that all optional items are shown using dashed lines, but rather those shown in dashed lines were chosen for a variety of reasons (e.g., they could be easily shown, to provide greater clarity, etc.). 
     References in the specification to “one embodiment”, “an embodiment”, “an example embodiment”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. 
     In the following description and claims, the terms “coupled” and “connected,” along with their derivatives, may be used. It should be understood that these terms are not intended as synonyms for each other. Rather, in particular embodiments, “connected” may be used to indicate that two or more elements are in direct physical or electrical contact with each other. “Coupled” may mean that two or more elements are in direct physical or electrical contact. However, “coupled” may also mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other. 
     In some cases, the operations of flow diagrams are described with reference to the exemplary embodiments of the other block diagrams. However, it should be understood that the operations of the flow diagrams can be performed by embodiments of the invention other than those discussed with reference to these other block diagrams, and that the embodiments of the invention discussed with reference to these other block diagrams can perform operations different than those discussed with reference to the flow diagrams. 
     The techniques shown in the figures can be implemented using code and data stored and executed on one or more computers. Such computers store and communicate (internally and with other computers over a network) code and data using machine-readable media, such as machine storage media (e.g., magnetic disks; optical disks; random access memory; read only memory; flash memory devices) and machine communication media (e.g., electrical, optical, acoustical or other form of propagated signals—such as carrier waves, infrared signals, digital signals, etc.). In addition, such computers typically include a set of one or more processors coupled to one or more other components, such as a storage device, a number of user input/output devices (e.g., a keyboard and a display), and a network connection. The coupling of the set of processors and other components is typically through one or more busses and bridges (also termed as bus controllers). The storage device and network traffic respectively represent one or more machine storage media and machine communication media. Thus, the storage device of a given computer system typically stores code and data for execution on the set of one or more processors of that computer. Of course, one or more parts of an embodiment of the invention may be implemented using different combinations of software, firmware, and/or hardware. 
     Overview 
     According to one aspect of the invention, a producer is at least a specific instance (or object) and a specific method, such that if the producer is executed during run time, the specific method is executed on the specific instance. Thus, a given producer is instantiated from a given instance and a given method associated with that instance. Like classes, instances, and methods, producers are basic elements or constructs manipulated by the runtime. Thus, the instantiation of a producer is interpreted and tracked by the runtime, and thus the runtime tracks the combination of instances and methods represented by producers. In other words, a producer is a runtime instantiatable construct that is tracked by the runtime, that is executed by the runtime, and that includes at least an instance and a method associated with that instance, such that the runtimes execution of the producer results in the method of the producer being executed on the instance of the producer. Also, the method of a producer has associated with it a producer dependency declaration that identifies, with a set of zero or more producer dependencies, a set of zero or more producers for the given producer. Specifically, producer dependencies are declared for methods using producer dependency declarations, the producer dependency declaration for a given method may include zero or more producer dependencies, and each producer dependency identifies a set of zero or more producers. Thus, producer dependency declarations and the producer dependencies they define are interpreted and tracked by the runtime, and thus the runtime tracks the relationships between producers indicated by the producer dependency declarations. 
     Where a given producer is dependent on a set of one or more other producers, the runtime will ensure execution of the set of other producers prior to the given producer. Thus, the producer dependency declarations represent execution relationships between producers, while producers represent operations to be performed (methods) and instances. While in some embodiments of the invention allow dependencies of parent producers on child producers to be declared in the producer dependency declaration associated with the method of the parent producer (the producer dependency declaration of the parent producer identifies any child producers—referred to herein as downwardly declared), other embodiments of the invention also allow dependencies to be declared in the producer dependency declaration associated with the method(s) of child producer(s) (the producer dependency declaration of the child producer identifies one or more parent producers—referred to herein as upwardly declared). 
     In different embodiments of the invention a producer identifies additional things. For example, while in some embodiments of the invention a producer is at least an instance and method associated with that instance, in other embodiments of the invention a producer is a class, an instance of that class, and a method associated with that instance (e.g., a producer may directly include a class, instance, and method; a producer may directly include an instance and a method, while indirectly identifying a class of that instance through a reference (e.g., a reference in the instance)). While the invention may be used in the context of code written in different programming languages (e.g., object-oriented code written in a reflective object-oriented language; object-oriented code written in a reflective object-based language; code written in a procedural, non-reflective object-oriented, non-reflective object-based language and transformed into reflective object-oriented language code), embodiments of the invention will be described, by way of example and not limitation, with reference to reflective object-oriented programming languages and with reference to producers that directly include classes, instances and methods. Also, while in one embodiment of the invention the method of a producer is an instance method (a method that can use instance fields in addition to any inputs received as arguments), alternative embodiments of the invention may also or alternatively support the method of a producer being a class method (methods that receive all inputs as arguments and/or uses instance independent variables) (where the method of a producer is an instance method, the instance of that producer is an instance of a class; while where the method of a producer is a class method, the instance of that producer is a meta-class instance representing the class). 
       FIG. 1A  is a block diagram illustrating the relationship of a producer dependency declaration for a method of a class in object oriented-source code to a producer that includes the class, a given instance of that class, and a method of that class, according to one embodiment of the invention. In  FIG. 1A , object-oriented source code  100  is shown including a class  102 , which in turn includes a method  104 , execution mode settings  105 , and a producer dependency declaration  106  for the method  104 . Of course, the class  102  would typically include one or more fields (not shown) and additional methods (not shown). In addition, the object-oriented source code  100  would typically include additional classes. 
     During run time, an instance  108  of the class  102  is instantiated. The instance  108  includes the data of the fields of the class  102 . In addition, a producer  110  is instantiated, where the producer  110  identifies the class  102 , the instance  108  of the class  102  (which has associated with it the method  104  of the class  102 ), and the method  104  of the class  102 . The producer dependency declaration  106  identifies to the runtime a set of zero or more producers  112  (referred to as child producers of the producer  110 ) that must be executed before execution of the producer  110 . In other words, the producer  110  depends on the set of zero or more producers  112 . In addition to or instead of consuming outputs of the set of producer  112 , the producer  110  may consume data of the instance  108 . In addition, the producer  110  provides at least one output, which output may be internal to the instance  108  (and thus, modify the data of the instance  108 ) and/or may be external; either way, the output of the producer  110  may be consumed by a set or zero or more other producers  114  (referred to as parent producers of the producer  110 )). As indicated previously, and described in more detail later herein, the producer dependency declaration  106 , in some embodiments of the invention, may also identify to the runtime zero or more of the producers  114 . 
     It should be understood that the inputs and outputs of producers are based on the inputs and outputs of the methods on which those producers are based. As such, these input and outputs may represent multiple parameters having a variety of data structures. 
     The producer dependency declaration for a given method identifies at run time the set of zero or more producers to be instantiated and executed. By way of example, where a producer dependency declaration (e.g., producer dependency declaration  106 ) for a given method (e.g., method  104 ) identifies a producer dependency on a given producer (which given producer identifies a first class, a first instance of that class, and a first method of that first class) (e.g., one of the set of producers  112 ), then the producer dependency declaration of the given method identifies to the runtime that the first instance is to be instantiated (if not already) and that the first method is to be used to instantiate the given producer for the first instance (in these examples, first does not mean location or order). 
     In operation, when, during run time, a given set of one or more producers are designated as being of interest and have producer dependencies declared for them, the runtime: 1) automatically generates (discovers, builds, and optionally resolves) a set of one or more graphs, which may be multi-level and may be of a variety of shapes (e.g., chain, tree), from the given set of producers designated as being of interest down to source producers based on the producer dependency declarations  106 ; and 2) sequences execution of producers of the set of graphs to generate the output(s) of the given set of producers designated as being of interest. Thus, the runtime uses the producer dependency declarations  106  to determine what methods with what arguments to execute, on what instances, and when for synchronization purposes. 
     In some embodiments, the runtime checks the execution mode setting  105  to determine the execution mode of a producer. Different execution modes may be supported in different systems. Some examples of execution modes include multithreading, multi-processing, and local execution. 
     Producer dependencies represent the sequencing of execution of producers to the runtime. However, in addition to indicating the sequencing of execution, producer dependencies may represent different input to output relationships in different embodiments of the invention. For example, different embodiments of the invention may support one or more of argument producer dependencies, field producer dependencies, and sequencing only producer dependencies (sequencing only producer dependencies are referred to herein with the shorthand sequencing producer dependencies). While each of argument producer dependencies, field producer dependencies, and sequencing producer dependencies represent execution sequencing relationships between producers, argument and field producer dependencies additionally represent data of which the runtime is aware. Specifically, an argument producer dependency causes the runtime to map the output of a child producer as an input parameter to a parent producer, whereas a field producer dependency indicates use of a field of an instance. Regardless of the input to output relationship represented by a producer dependency, proper use of producer dependencies ensures that the producers accessing information are sequenced after the producers that impact that information. 
     Sequencing dependencies may be used for a variety of purposes, including ensuring the order of execution between producers that modify data in a manner of which the runtime is not aware and producers that consume that data (a child producer may write its outputs in a way that requires the method of the parent producer to include code to access that output (e.g., a method that impacts the environment by affecting an output that is not the regular producer output and, as such, that is not detected by the runtime—such as a method that sets a global variable, that sets a field in an instance which is not the producer output, that impacts an external data source, etc.)) Thus, a sequencing dependency reflects a dependency of a parent producer on a child producer, but requires outputs that need to be provided, if any, from one to the other occur through the writing of code (e.g., code in the method of the child producer to write an output to a given mechanism (such as set a global variable, impact an external data source, set a field of an instance which is not the producer output, etc.) and code in the method of the parent producer to read that output from the given mechanism). In this way, sequencing dependencies allow the runtime to synchronize execution of any parent producers that rely on an output that the runtime cannot detect. 
     In one embodiment of the invention the producer dependency declaration  106  for a given method identifies only direct dependencies on producers (e.g., direct descendents (children), in contrast with indirect descendents (grand-children, great grand-children, etc.)). In such an embodiment, each producer dependency declaration provides only a single tier or layer of producers whose outputs may be used directly by a producer instantiated from the given method; leaving discovery/building/resolution of additional layers of the producer graph(s) to the runtime&#39;s processing of other producer dependency declarations. 
     According to one embodiment of the invention, the dependencies of producers identified by the producer dependency declaration  106  are useful in implementing parallelization and instrumentation of the application program including the producers. To parallelize the application program, two or more producers of the application program are executed substantially at about the same time in the same execution mode or in different execution modes. To instrument the application, metrics of the producers are acquired as the producers are being executed. Details of parallelization and instrumentation are further discussed below with reference to exemplary embodiments of the invention. 
     Exemplary Keys 
     A producer can be viewed as a set of multiple identifiers, one identifier for each additional level of granularity specified (class, instance, method, etc.). In addition, some embodiments of the invention implement each identifier as a separate key, while other embodiments have certain identifiers share a key. By way of example, some embodiments of the invention implement a producer as a class, instance, and method triplet and implement keys, such that each part of the triplet is identified by a separate key (a class key, instance key, and method key) and the producer is identified by the combination of the class key, instance key, and method key (the producer key). 
     Embodiments of the invention that use keys may vary in the uniqueness of the keys used. For example, in one embodiment of the invention, each class key is unique, each instance key is unique across all instances of all classes, and each method key is unique across all methods of all classes. As another example, in other embodiments of the invention, each class has a unique key, each instance of a given class has a unique key (across the class instances), and each method of a class has a unique key (across the class methods); but instances of different classes may have the same instance key, and methods of different classes may have the same method key; this later approach will be used in the remainder of the document by way of example and not limitation. For example, assume a first class includes methods and has a key for each of these methods that is unique within the first class, then the instances of this class (which will each have a unique key as to each other) have the same method keys associated with them. As another example, assume a different second class includes methods (be some, all, or none the same as the methods of the first class) that have the same method keys as those used for the first class; as such, an instance of this different class may have associated with it the same method keys as associated with an instance of the first class. 
     The use of keys allow for a variety of features, including: 1) the tracking of each entity identified by a producer&#39;s identifiers (e.g., the tracking of each class, instance, and method); 2) several parent producers (unaware of their mutual existence) to connect to the same child producer based on their producer dependency declarations (which specify producer dependencies using the producer keys); etc. In one embodiment of the invention, the instance key is an instance of a class (InstanceKey) holding two elements: an instance key nature indicating if the key identifier is a reference to the instance or another object (such as a string), and a key identifier which can either be a reference to the instance, or another object (such as a string). The storing of an instance reference in the instance key spares the programmer from inventing a name to identify these instances. 
     Exemplary Relationships 
     In the context of the above discussion regarding a producer being viewed as a set of multiple identifiers (with one identifier for each additional level of granularity specified), in one embodiment of the invention the various supported relationships between a producer and its children and parents are those in which at least one such identifier is different between a producer and its set of zero or more parent producers and one such identifier is different between a producer and each of its set of zero or more child producers. By way of providing some exemplary relationships, assume that a first producer is instantiated, where the first producer is a first instance of a first class and a first method of that first class, and assume that the producer dependency declaration for that first method identifies at run time a second producer as a child, then the second producer may be: 1) the first instance of the first class and a second method of that first class; 2) a second instance of the first class and a second method of that first class; or 3) a second instance of the first class and the first method of the first class; or 4) an instance of a second class and a method of that second class. In such case, the first producer is dependent on the second producer—thus, representing an input to output relationship of the first producer on the second producer. Various relationships and combinations of those relationships are described below for one embodiment of the invention that uses an object-oriented language and in which a producer identifies at least a class, instance, and method. 
       FIGS. 1B-1D  illustrate exemplary relationships between a given producer, its set of parent producers, and its set of child producers according to one embodiment of the invention.  FIGS. 1B-1D  each show the following: 1) a class definition  102 A including methods  104 A-C and producer dependency declarations  106 A-C for each of those methods, respectively; 2) a class definition  102 B including methods  104 D-E and producer dependency declarations  106 D-E for each of those methods, respectively; 3) a class definition  102 C including method  104 F and producer dependency declaration  106 F for that method; 4) an instance  108 A of the class  102 A; 5) a producer  110 A that identifies the class  102 A, the instance  108 A, and the method  104 A; and 6) a producer  112 A. 1  and a producer  114 A. 1  respectively representing one of the set of producers  112  and  114 . Dashed lines with boxed letters on them are used in  FIGS. 1B-1D  to illustrate the exemplary relationships. Thus, the collection of dashed lines with a boxed A on them represent one relationship. The relationships in  FIG. 1B  are combinable with the relationships in  FIG. 1C ; as such, these combinations represent combinations of relationships between parent producers  114 A and child producers  112 A to producer  110 A. Further,  FIG. 1D  illustrates some additional exemplary combinations of relationships between parent producers  114 A and child producers  112 A to producer  110 A. 
       FIG. 1B  illustrates exemplary relationships between the producer  110 A and the parent producer  114 A. 1  according to one embodiment of the invention.  FIG. 1B  additionally includes an instance  108 B. The set of producers  114  is identified by other producer dependency declarations of different method(s) of the same class, different instances of the same class, and/or method(s) of a different class; and thus, each of the set of producers  114  may be: 1) of the same instance as the producer  110 A (instance  108 A of class  102 A) and a different method of that instance (illustrated by the boxed A on the dashed lines from the instance  108 A to the producer  114 A. 1  and from the method  104 B to the producer  114 A. 1 ); 2) of a different instance of the class  102 A and a different method of that instance (illustrated by the boxed B on the dashed lines from the class  102 A to the instance  108 B, from the instance  108 B to the producer  114 A. 1 , and from the method  104 B to the producer  114 A. 1 ); 3) of an instance of a different class and a method of that instance (illustrated by the boxed C on the dashed lines from the class  102 B to the instance  108 B, from the instance  108 B to the producer  114 A. 1 , and from the method  104 D to the producer  114 A. 1 ); or 4) of a different instance of class  102 A (than instance  108 A) and the same method (method  104 A) of that instance (e.g., with a contingent dependency—described later herein) (illustrated by the boxed D on the dashed lines from the class  102 A to the instance  108 B, from the instance  108 B to the producer  114 A. 1 , and from the method  104 A to the producer  114 A. 1 ); further, where there are multiple producers in the set of producers  114 , the producers  114  themselves may be part of the same instance of the class  102 A, different instances of the class  102 A, the same instance of a different class, different instances of a different class, and/or a mixture of the above. 
       FIG. 1C  illustrates exemplary relationships between the producer  110 A and the child producer  112 A. 1  according to one embodiment of the invention.  FIG. 1C  additionally includes an instance  108 C. Each of the set of producers  112 A may be: 1) of the same instance as the producer  110 A (instance  108 A of class  102 A) and a different method of that instance (illustrated by the boxed E on the dashed lines from the instance  108 A to the producer  112 A. 1  and from the method  104 C to the producer  112 A. 1 ); 2) of a different instance of the class  102 A and a different method of that instance (illustrated by the boxed F on the dashed lines from the class  102 A to the instance  108 C, from the instance  108 C to the producer  112 A. 1 , and from the method  104 C to the producer  112 A. 1 ); 3) of an instance of a different class and a method of that instance (illustrated by the boxed G on the dashed lines from the class  102 C to the instance  108 C, from the instance  108 C to the producer  112 A. 1 , and from the method  104 F to the producer  112 A. 1 ); or 4) of a different instance of class  102 A (than instance  108 ) and the same method (method  104 A) of that instance (e.g., with a contingent dependency described later herein) (illustrated by the boxed H on the dashed lines from the class  102 A to the instance  108 C, from the instance  108 C to the producer  112 A. 1 , and from the method  104 A to the producer  112 A. 1 ). Thus, each of the set of producers  112 A may be of the same instance as the producer  110 A, of a different instance of the class  102 A, or an instance of a different class; further, where there are multiple producers in the set of producers  112 A, the producers  112 A themselves may be part of the same instance of the class  102 A, different instances of the class  102 A, the same instance of a different class, different instances of a different class, and/or a mixture of the above. 
       FIG. 1D  illustrates some additional exemplary combinations of relationships of parent producers  114  and child producers  112  to producer  110 A according to one embodiment of the invention.  FIG. 1D  additionally includes the instance  108 B and the instance  108 C. The combinations of  FIG. 1D  are shown in Table 1 below: 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Boxed 
                 Dashed Lines For Parent Producer 
                 Dashed Lines For Child Producer 112A.1 
               
               
                 Letter 
                 114A.1 from 
                 from 
               
               
                   
               
             
            
               
                 I 
                 From instance 108A to producer 
                 From instance 108A to producer 112A.1 
               
               
                   
                 114A.1 and from method 104B to 
                 and from method 104B to producer 112A.1 
               
               
                   
                 producer 114A.1 
                   
               
               
                 J 
                 From instance 108A to producer 
                 From class 102A to instance 108C, from 
               
               
                   
                 114A.1 and from method 104B to 
                 instance 108C to producer 112A.1, and 
               
               
                   
                 producer 114A.1 
                 from method 104B to producer 112A.1 
               
               
                 K 
                 From class 102A to instance 108B, 
                 From instance 108A to producer 112A.1 
               
               
                   
                 from instance 108B to producer 
                 and from method 104B to producer 112A.1 
               
               
                   
                 114A.1, and from method 104B to 
                   
               
               
                   
                 producer 114A.1 
                   
               
               
                 L 
                 From class 102B to instance 108B, 
                 From class 102B to instance 108B, from 
               
               
                   
                 from instance 108B to producer 
                 instance 108B to producer 112A.1, and 
               
               
                   
                 114A.1, and from method 104E to 
                 from method 104E to producer 112A.1 
               
               
                   
                 producer 114A.1 
                   
               
               
                 M 
                 From class 102B to instance 108B, 
                 From class 102B to instance 108C, from 
               
               
                   
                 from instance 108B to producer 
                 instance 108C to producer 112A.1, and 
               
               
                   
                 114A.1, and from method 104E to 
                 from method 104E to producer 112A.1 
               
               
                   
                 producer 114A.1 
                   
               
               
                 N 
                 From class 102A to instance 108B, 
                 From class 102A to instance 108C, from 
               
               
                   
                 from instance 108B to producer 
                 instance 108C to producer 112A.1, and 
               
               
                   
                 114A.1, and from method 104A to 
                 from method 104A to producer 112A.1 
               
               
                   
                 producer 114A.1 
                   
               
               
                 O 
                 From class 102A to instance 108B, 
                 From class 102A to instance 108B, from 
               
               
                   
                 from instance 108B to producer 
                 instance 108B to producer 112A.1, and 
               
               
                   
                 114A.1, and from method 104A to 
                 from method 104A to producer 112A.1 
               
               
                   
                 producer 114A.1 
                   
               
               
                 P 
                 From instance 108A to producer 
                 From class 102A to instance 108C, from 
               
               
                   
                 114A.1 and from method 104B to 
                 instance 108C to producer 112A.1, and 
               
               
                   
                 producer 114A.1 
                 from method 104A to producer 112A.1 
               
               
                 Q 
                 From class 102A to instance 108B, 
                 From class 102A to instance 108B, from 
               
               
                   
                 from instance 108B to producer 
                 instance 108B to producer 112A.1, and 
               
               
                   
                 114A.1, and from method 104A to 
                 from method 104B to producer 112A.1 
               
               
                   
                 producer 114A.1 
                   
               
               
                 R 
                 From class 102B to instance 108B, 
                 From class 102B to instance 108B, from 
               
               
                   
                 from instance 108B to producer 
                 instance 108B to producer 112A.1, and 
               
               
                   
                 114A.1, and from method 104D to 
                 from method 104E to producer 112A.1 
               
               
                   
                 producer 114A.1 
               
               
                   
               
            
           
         
       
     
       FIG. 1E  illustrates that different instances of the same class can have producers based on the same and/or different methods according to one embodiment of the invention.  FIG. 1E  shows: 1) the class definition  102 A including methods  104 A-C and producer dependency declarations  106 A-C for each of those methods, respectively; 2) the instance  108 A and the instance  108 B being of class  102 A; 3) a producer  110 A is the method  104 A of the instance  108 A of the class  102 A; 4) a producer  110 B is the method  104 B of the instance  108 A of the class  102 A; 5) a producer  110 C is the method  104 A of the instance  108 B of the class  102 A; and 6) a producer  110 D is the method  104 C of the instance  108 B of the class  102 A. In addition,  FIG. 1D  shows that: 1) the producer dependency declaration  106 A for method  104 A identifies at run time the child producers of both the producer  110 A and the producer  110 C; 2) the producer dependency declaration  106 B for method  104 B identifies at run time the child producer of producer  110 B; and 3) the producer dependency declaration  106 C for method  104 C identifies at run time the child producer of producer  110 D. 
     Exemplary Runtimes 
       FIG. 2  is a block diagram illustrating the reusability of a runtime with producer graph oriented programming support according to one embodiment of the invention. In  FIG. 2 , multiple object-oriented application programs (object-oriented application code with producer dependency declarations  210 A-I) are run by the same runtime with producer graph oriented programming support  220 . 
       FIG. 3A  is a block diagram illustrating a runtime with producer graph oriented programming support according to one embodiment of the invention. In  FIG. 3A , a runtime with producer graph oriented programming support  335  includes an automated producer graph generation module  340  and a producer graph execution module  345 . In addition, the runtime  335  is to execute object-oriented source code, and thus includes additional modules not shown. 
     In addition,  FIG. 3A  shows producer dependency declarations for methods in object-oriented source code  320 , a current set of one or more producers whose outputs are of interest  325  (also referred to here as the currently selected producers of interest), and the outputs of source producers  330  (described later herein). The automated producer graph generation module  340  receives the producer dependency declarations  320  and the current set of producers of interest  325 . 
     The automated producer graph generation module  340  attempts to discover, based on the producer dependency declarations, child producers with outputs that contribute directly and indirectly to the input of the currently selected producers of interest, and build a current graph of producers representing the input dependency of these producers on each other from the currently selected producers of interest to those of the discovered producers that are source producers. The producer graphs(s) are stored in the producer graph(s) structure  380 . 
     The producer graph execution module  345  receives the current producer graph(s) from the automated producer graph generation module  340  and the outputs of source producers  330 , and executes the producers of the current producer graph(s) to determine the current output of the currently selected producers of interest. In some embodiments, the producer graph execution module  345  includes a parallelization module  3451 , a multiprocessing module  3453 , a multithreading module  3455 , and a local execution module  3457 . The parallelization module  3451  may determine the execution mode of a producer and send the producer to one of the multiprocessing module  3453 , the multithreading module  3455 , and the local execution module  3457  to be executed in the execution mode determined Parallelization may be supported by an individual execution mode. For instance, parallel execution of producers may be accomplished by the multiprocessing module  3453  using multiprocessing. Alternatively, parallel execution of producers may be accomplished by the multithreading module  3455  using multithreading. Furthermore, parallelization may be supported by a combination of execution modes. In other words, producers may be executed in parallel using different execution modes. For instance, two producers may be executed in parallel by sending one producer to the multithreading module  3455  and the other producer to the local execution module  3457 . It should be appreciated that other combinations of execution modes may be used to implement parallelization. 
     The producer graph execution module  345  caches the current outputs of the producers in the producer graph structure  380  as illustrated by the producer output caching  384 . The caching of producer outputs of the producer graph during execution allows for synchronization. For instance, the appropriate time to execute a parent producer that is dependent on multiple child producers is after all of the multiple child producers have been executed; in other words, it would be wasteful (and, in some cases, not possible) to execute the parent producer each time one of its child producers completed execution. The caching of the producer outputs allows for the execution of the parent producer to not only be postponed until all its child producers have been executed, it also allows for a determination of the appropriate time for the execution of the parent producer—when all of the child producers have been executed and their outputs have been cached. Thus, the runtime makes this synchronization decision for the programmer by checking the availability of the needed outputs in the producer output caching  384 ; in other words, such synchronization is automated (the programmer need not include separate source code that determines the appropriate time to execute a given method of an instance). By way of another example, where several parent producers are dependent on the same child producer as well as on other different child producers, the appropriate time to execute each of the several parent producers is typically different; the runtime automatically determines the appropriate time to execute each of the several parent producers depending on the availability of the outputs of its set of child producers. 
     As will be described in more detail later herein, since some parts of a producer graph may not be currently discoverable due to dynamic producer dependencies, the automated producer graph generation module  340  “attempts” to discover and build the entire producer graph, but may not initially be able to complete the entire producer graph until some producers are executed. As such, the producer graph execution module  345  may invoke the automated producer graph generation module  340  with needed producer outputs during execution of the current producer graph to complete any unresolved remainders of the current producer graph (this is illustrated in  FIG. 3A  by a dashed arrowed line from the producer graph execution module  345  to the automated producer graph generation module  340 ; a dashed arrowed line is used because such support is optional) 
       FIG. 4A  is a block diagram illustrating the discovery and building of an exemplary producer graph according to one embodiment of the invention.  FIG. 4A  shows that the current set of producers of interest consists of producer  1 . Based upon producer  1  and its producer dependency declaration, producer  2  and producer  3  are discovered. In other words, the producer dependency declaration for producer  1  identifies that the input to producer  1  requires execution of producer  2  and producer  3 . As such, producer  1  is a dependent producer (a producer that has one or more producer dependencies).  FIG. 4A  also shows that while producer  3  is an independent producer (a producer that has no producer dependencies, and thus is a source producer), producer  2  is not. As a result, based upon the producer dependency declaration of producer  2 , producer  4  and producer  5  are discovered. In  FIG. 2A , producer  4  and producer  5  are independent producers (and thus, source producers). 
       FIG. 4B  is a block diagram illustrating the initial execution of the producer graph of  FIG. 4A  according to one embodiment of the invention. In  FIG. 4B , curved arrowed lines illustrate the execution of one producer to generate an output that is provided as the input to another producer. As shown in  FIG. 3A , the output of the source producers  330  are provided to the producer graph execution module  345 ; in contrast, the outputs of the dependent producers  1 - 2  are determined by execution of those producers as shown in  FIG. 4B . Thus, in  FIG. 4B , the following occurs: 1) the output of source producer  4  and source producer  5  are provided to dependent producer  2 ; 2) dependent producer  2  is executed; 3) the outputs of dependent producer  2  and source producer  3  are provided to producer  1 ; and 4) producer  1  is executed and its output is provided as the current output of interest. It is worth noting that the producer graph of  FIG. 4B  is data driven in the sense that data flows from one producer to another producer up the graph. 
     In some embodiments, producer  4  and producer  5  may be executed in parallel using different execution modes or a single execution mode that supports parallelization (e.g., multiprocessing, multithreading, etc.) because producer  4  and producer  5  are independent of each other. However, since producer  2  depends on producers  4  and  5  in the current example, producer  2  may not be executed in parallel with producers  4  and  5 . Thus, the runtime may wait for producers  4  and  5  to be done before executing producer  2 . As for producer  3 , since producer  3  is independent of producers  4  and  5 , producer  3  may be executed in parallel with producers  4  and  5 . Alternatively, producer  3  may be executed in parallel with producer  2  because producer  3  is also independent of producer  2 . In some embodiments, execution of producer  3  may overlap in time with the execution of producers  4  and  5 , as well as the execution of producer  2 , depending on how long it takes to execute producers  3 ,  4 , and  5 . 
     Thus, the producer dependency declarations  320  bound the possible producer graphs that may be generated; while the currently selected set of producers of interest  325  identify the beginning node(s) of the current producer graph to be generated. From these two, the automated producer graph generation module  340  discovers and builds the producer graph. The discovery and building is automated in that the automated producer graph generation module  340  is not provided the producer graph (e.g., it does not need to be manually identified by a programmer) or even a list of the producers that will be in the producer graph. Rather, the automated producer graph generation module  340  parses the producer dependency declaration(s) of the current selected set of producers of interest to discover their discovered producers, then parses the producer dependency declarations of those discovered producers, and so on down to the source producers (in some embodiments of the invention described later herein, this may be done with the assistance of the producer graph execution module  345 ). In the case where the producer graph is a tree, a currently selected producer of interest will typically be the root node, and the producer dependency declarations will be parsed until the leaf nodes (source producers) are discovered. 
     Overridden Producers and Incremental Execution 
       FIG. 3B  is a block diagram illustrating a runtime with producer graph oriented programming support that also supports incremental execution and overridden producer outputs according to one embodiment of the invention. It should be understood that incremental execution and overridden producer outputs are each independent optional features, and thus different embodiments of the invention may implement one or both. Although not explicitly illustrated in  FIG. 3B , one should appreciate that the parallelization modules  3451 , the multiprocessing module  3453 , the multithreading module  3455 , and the local execution module  3457  in  FIG. 3A  may be included in the producer graph execution module  370  in  FIG. 3B  to allow the producer graph execution module  370  in  FIG. 3B  to implement parallelization in the execution of producers. 
     In  FIG. 3B , a runtime with producer graph oriented programming support  360  includes an automated producer graph generation module  365 , a producer graph execution module  370 , and an override producer output module  390 . The runtime  360  is to execute object-oriented source code, and thus includes additional modules not shown. 
     In addition,  FIG. 3B  shows the producer dependency declarations for methods in object-oriented source code  320 , the current set of one or more producers whose outputs are of interest  325  (also referred to herein as the currently selected producers of interest), and the output of source producers  350 . The output of source producers  350  includes the outputs of independent producers set in the source code  352  (e.g., constants, default values, etc.) and the currently overridden producer outputs  354  (the outputs of the independent producers and/or dependent producers whose outputs are currently overridden). 
     In some embodiments of the invention, the outputs of producers may be explicitly overridden with a currently provided value (i.e., rather than executing a producer to determine its output value based on its current inputs, the output value for the producer is explicitly provided). In addition to any independent producers of a producer graph, the source producers of a producer graph include any currently overridden producers. 
     The override producer output module  390  receives the overridden producer outputs  354  (which identify which producers are being overridden and what output values they are being overridden with). In one embodiment of the invention, producers can be classified as property producers or method producers. Property producers are those based on property methods (e.g., get and set). Method producers are those based on non-property methods. The override producer output module  390  includes an override property producer output module  392  for overridden property producers and an override method producer output module  394  for overridden method producers. The override property producer output module  392  causes the overridden value to be stored in the producer output caching  384  and in the data of the instance, whereas the override method producer output module  394  causes the overridden value to be stored in the producer output caching  384 . Depending on the embodiment of the invention, this causation may be direct or indirect.  FIG. 3B  illustrates an indirect causation through the use of an override log  396  which collects the output of the override producer output module  390  and which is consumed by the producer graph execution module  370 . For optimization purposes, the override log  396  allows for the delaying of overrides in order to collect multiple overrides for batch processing. 
     Similar to the automated producer graph generation module  340 , the automated producer graph generation module  365 : 1) receives the producer dependency declarations  320  and the current set of producers of interest  325 ; and 2) attempts to discover, based on the producer dependency declarations, producers with outputs that contribute directly and indirectly to the input of the currently selected producers of interest, and build a current graph of producers representing the input dependency of these producers on each other from the currently selected producers of interest, through any discovered non-source producers, to those of the discovered producers that are source producers (independent producers and currently overridden producers). The producer graphs(s) are stored in the producer graph(s) structure  380 . 
     Similar to the producer graph execution module  345 , the producer graph execution module  370  receives the current producer graph from the automated graph module  365  and the outputs of source producers  350 , and executes the producers of the current producer graph to determine the current output of the currently selected producers of interest. The producer graph execution module  370  caches the current outputs of the producers in the producer graph structure  380  as illustrated by the producer output caching  384 . 
     As previously described, the caching of producer outputs during execution allows for synchronization (e.g., separate source code need not be written to determine when producer  2  of  FIG. 4B  should be executed, but rather the runtime makes this synchronization decision for the programmer by checking the availability of the needed outputs in the producer output caching  384 ; in other words, such synchronization is automated). Furthermore, the caching of producer outputs during execution may allow parallelization of producer execution because the runtime may decide which producer is ready for execution by checking the availability of the needed outputs in the producer output caching  384 . Producers that are ready for execution may be executed in parallel. In other words, parallelization may be automated as well. Thus, no separate source code is needed to determine or to indicate which producers should be executed in parallel. In addition, this producer output caching  384  is used for incremental execution. More specifically, after a producer graph has been initially generated and executed, the overriding of a producer in the current producer graph requires some level of reexecution. While some embodiments of the invention simply reexecute the entire graph, alternative embodiments of the invention support incremental execution (reexecuting only those parts of the producer graph that are affected by the override). Some exemplary embodiments that support incremental execution use incremental execution marking  382  in the producer graph(s) structure  380  to help determine which producers require reexecution. Thus, maintaining the producer graph refers to modifying the links of the producer graph as necessary across multiple executions, to keep them current (up to date), whereas incremental execution refers to both maintaining the producer graph(s) and using the current (up to date) producer graph(s) to re-execute only those parts of the producer graph(s) that are affected by an override. 
     Similar to  FIG. 3A , there is a dashed arrowed line from the producer graph execution module  370  to the automated producer graph execution module  365  to represent optional support for dynamic dependencies. It should be noted that dynamic dependencies may change during reexecution of a producer graph. 
       FIG. 4C  is a block diagram illustrating the incremental execution of the producer graph of  FIG. 4B  according to one embodiment of the invention. In  FIG. 4C , the output of producer  5  has been explicitly modified, but the outputs of producer  3  and producer  4  have not. Based upon the tracking of output to input dependencies in the producer graph and that only the output of producer  5  has been explicitly modified, it is determined that only producer  2  and producer  1  are affected by this modification. As a result, the determination of an updated output of producer  1  requires only the reexecution of producer  2  and producer  1  with the new output of producer  5  and the prior outputs of producer  4  and producer  3 . This partial reexecution of the producer graph is illustrated in  FIG. 4C  by curved arrowed lines from producer  5  to producer  2  and from producer  2  to producer  1 , but not from producer  4  to producer  2  or from producer  3  to producer  1 . The lack of curved arrowed lines from producer  4  to producer  2  and from producer  3  to producer  1  are not to indicate that the outputs of producer  3  and producer  4  are not needed, but rather that producer  3  and producer  4  need not be reexecuted if their prior output is available. (e.g., cached from the prior execution of the producer graph). 
     The relatively simple example of  FIG. 4C  illustrates that there can be a savings in processing resources as a result of incremental execution. Such savings depend on a number of factors (e.g., the number of producers that do not need to be reexecuted, the amount of processing those producers would have required, etc.). While one embodiment of the invention is illustrated that performs incremental execution, alternative embodiments may be implemented differently (e.g., an alternative embodiment may reexecute all producers responsive to a modification). 
       FIG. 4D  is a block diagram illustrating the incremental execution of the producer graph of  FIG. 4B  after dependent producer  2  has been overridden according to one embodiment of the invention. In  FIG. 4D , the output of producer  2  has been explicitly modified, but the output of producer  3  has not. Based upon the producer graph and that only the output of producer  2  has been explicitly modified, it is determined that only producer  1  is affected by this modification. As a result, the determination of an updated output of producer  1  requires only the reexecution of producer  1  with the overridden output of producer  2  and the prior output of producer  3 . This partial reexecution of the producer graph is illustrated in  FIG. 4D  by a curved arrowed line from producer  2  to producer  1 , but not from producer  4  and  5  to producer  2  or from producer  3  to producer  1 . 
       FIG. 4E  is a block diagram illustrating the incremental execution of the producer graph of  FIG. 4B  after dependent producer  2  has been overridden and independent source producer  3  has been modified according to one embodiment of the invention. Based upon the producer graph and that only the outputs of producer  2  and producer  3  have been modified, it is determined that only producer  1  is affected by this modification. As a result, the determination of an updated output of producer  1  requires only the reexecution of producer  1  with the overridden output of producer  2  and the modified output of producer  3 . This partial reexecution of the producer graph is illustrated in  FIG. 4E  by a curved arrowed line from producers  2  and  3  to producer  1 , but not from producers  4  and  5  to producer  2 . 
     While one embodiment of the invention that supports overriding producer outputs also supports unoverriding producer outputs, alternative embodiments of the invention do not. While one embodiment of the invention that supports unoverriding producers leaves an overridden producer overridden until it is specifically unoverridden, alternative embodiments of the invention may be implemented differently (e.g., unoverriding an overridden producer when one of its progeny is overridden). 
     In one embodiment of the invention the producer graph oriented programming framework includes an external interface used to interface with programs not written with producer dependency declarations. This external framework includes: 1) a caller part (referred to as the runtime client); and 2) a called part (referred to as an external data source). If a producer reads data directly from an external data source, it may just read the data when the producer is created, just read the data when instructed to do so (manual refresh), or subscribe to it. In the case of manual refresh and subscription, changes in the external data source would result in the set method of the producer being invoked and the modification of the output of the producer (treated the same as an overridden producer). 
     Producer Graph Building and Execution 
     Different embodiments of the invention may be implemented to discover and build out a producer graph to different extents (e.g., build the producer graph until all paths from the root node end at independent producers (in which case, the end nodes of a producer graph are independent producers, with the possibility of any overridden producers being intermediate nodes); build the producer graph out until each path from the root node ends in an overridden producer or an independent producer, whichever is reached first (in which case, each end node of a producer graph is either an independent producer or an overridden producer)). 
     “Execution start producers” refers to the producers of a producer graph from which a given execution of the producer graph begins. For an initial execution of a producer graph, different embodiments may start from different producers (e.g., in embodiments of the invention that build the producer graph until all paths from the root node end at independent producers, execution may start from the end nodes (which would be the independent producers), from the source producers (which would include the independent producer nodes and any overridden producer nodes), from a subset of the source producers consisting of the combination of any independent producers with at least one path between them and the root producer that does not include an overridden producer and any overridden producers, or from a subset of the source producers consisting of the combination of any overridden producers without any descendents that are overridden and any independent producers with at least one path between them and the root producer that does not include an overridden producer; in embodiments of the invention where the producer graph under overridden producers is not built if and until such a producer is un-overridden, execution may start from the end nodes (which may be independent producers and/or overridden producers), etc). 
     For subsequent executions of a producer graph, different embodiments may start from different producers (e.g., from the independent producers of the producer graph (e.g., in embodiments of the invention that do not support incremental execution); from the source producers of the producer graph (e.g., in embodiments of the invention that do not support incremental execution); from a subset of the source producers that consists of those source producers that have been overridden and/or added since the last execution (e.g., in embodiments of the invention that do support incremental execution); of the source producers that have been overridden and/or added since the last execution, from the combination of any such overridden producers without any descendents that are overridden and any such added producers with at least one path between them and the root producer that does not include an overridden producer (e.g., in embodiments of the invention that do support incremental execution); etc). 
     With regard to the above concept of execution start producers, the processing flow of execution of the producer graph also differs between different embodiments. For example, in one embodiment of the invention, the ancestry of the execution start producers are determined and placed in a collection, the execution start producers are executed, and the collection is iteratively scanned for producers for whom all dependencies have been executed—eventually the root nodes are reached. As another example, in one embodiment of the invention, the execution start producers are executed, the parents of the execution start producers are identified, those parents are executed, and their parents are identified and executed, and so on. The later embodiment of the invention is used below by way of example, and not limitation. 
     Exemplary Types of Dependencies 
     Exemplary Dynamic Producer Dependencies 
     A dynamic producer dependency is a producer dependency that can change during run time. It should be understood that the criteria for resolving the producer dependency is present in the source code, and thus the producers to which the producer dependency may be resolved are limited. With reference to  FIG. 3A , the dashed arrowed line from the producer graph execution module  345  to the automated producer graph generation module  340  represents support for the execution of one or more producers in the current producer graph that are necessary to discover and build the entire current producer graph. In other words, an embodiment of the invention that supports dynamic producer dependencies may iterate between the automated producer graph generation module  340  and the producer graph execution module  345  until the entire producer graph is discovered, built, resolved, and executed (that is, iterate between: 1) invoking the automated producer graph generation module to discover and build those parts of the current producer graph that can be resolved at that time; and 2) invoking the producer graph execution module to execute producers of the current producer graph). In this sense, discovering refers to the accessing of the producer dependency declarations and determining the producers they identify; building refers to instantiating the producers and adding them to the producer graph; and resolving refers to determining currently unresolved dynamic producer dependencies. 
       FIG. 5A  is a block diagram illustrating the discovery and building of an exemplary producer graph including an unresolved dependency according to one embodiment of the invention.  FIG. 5A  shows the current set of producers of interest consisting of producer  1 . Based upon producer  1  and its producer dependency declaration, producer  2  and producer  3  are discovered. In other words, the dependency declaration for producer  1  identifies that producer  1  requires as inputs the output of producer  2  and producer  3 .  FIG. 5A  also shows that while producer  3  is an independent producer (and thus, a source producer), producer  2  is not. As a result, based upon the dependency declaration of producer  2 , producer  4  and producer  5  are discovered. Further,  FIG. 5A  shows that while producer  4  is an independent producer (and thus, a source producer), producer  5  is not. As a result, based upon the dependency declaration of producer  5 , producer  6  and a currently unresolved dependency are discovered.  FIG. 5A  also shows that the currently unresolved dependency may be to producer  7 A and/or producer  7 B. 
       FIG. 5B  is a block diagram illustrating the initial execution of the producer graph of  FIG. 5A  and the resolution of the unresolved dependency according to one embodiment of the invention.  FIG. 5B  illustrates the producer graph of  FIG. 5A  with curved arrowed lines showing execution of the producers and provision of their outputs to dependent parent producers. In addition,  FIG. 5B  shows that the unresolved dependency of producer  5  is resolved as a dependency on producer  7 A, and that producer  7 A is an independent producer. Note that producer  7 A may be executed by itself, or be executed in parallel with producer  6 , or be executed in parallel with producer  4 , be executed in parallel with producer  3 , or be executed in parallel with any combination of producers  3 ,  4 , and  6 . Such parallel execution is allowed because producer  7 A is independent of producers  3 ,  4 , and  6 . 
       FIG. 5C  is a block diagram illustrating the initial execution of the producer graph of  FIG. 5A  and/or the reexecution of the producer graph of  FIG. 5B  according to one embodiment of the invention.  FIG. 5C  illustrates the producer graph of  FIG. 5A  with curved arrowed lines showing execution of the producers and provision of their outputs to dependent parent producers. In addition,  FIG. 5C  shows that the unresolved dependency of producer  5  is resolved as a dependency on producer  7 B and that producer  7 B is a dependent producer. As a result, based upon the dependency declaration of producer  7 B, producer  8  is discovered. Producer  8  is an independent producer (and thus, is a source producer). Assuming that  FIG. 5C  represents the initial execution of the producer graph of  FIG. 5A , all of the curved arrowed lines in  FIG. 5C  would be employed. However, assuming that  FIG. 5C  represents the reexecution of the producer graph of  FIG. 5B , the reexecution results in the dynamic dependency being resolved differently (a switch from producer  5  being dependent on producer  7 A to producer  7 B). Further, if the reexecution is performed without incremental execution, then all of the curved arrowed lines in  FIG. 5C  would be employed; however, if incremental execution was used, only the non-dashed curved arrowed lines would be employed (producer  8  to producer  7 B, producer  7 B to producer  5 , producer  5  to producer  2 , and producer  2  to producer  1 ). It should also be understood that the dynamic change in dependency illustrated in  FIG. 5C  is exemplary, and thus any number of different situations could arise (e.g., the dynamic change may never occur; producer  5  could have first been dependent on producer  7 B and then changed to producer  7 A; producer  5  could have first been dependent on producer  7 B and no dynamic change ever occurs; producer  5  could be found to be dependent on both producer  7 A and producer  7 B as illustrated in  FIG. 5D ; etc.) While different embodiments may resolve dynamic producer dependencies in different ways, some examples are provided later herein. 
     Thus, automated reexecution of a producer graph is not limited to the producer being modified and its direct parent being reexecuted; rather a change is automatically rippled through the producer graph by the runtime, affecting any appropriate producers and dependencies, because the producer graphs are maintained (and incremental execution is used where supported). As such, changes cause any necessary additional discovery, building, resolving, and executing. Thus, the reexecution of a producer graph is automated in the sense that a user/programmer need not determine which producers of the producer graph are affected and possibly manually correct the graph. 
     Static Producer Dependencies 
     A static dependency is one that cannot change during run time. Thus, in an embodiment that supports contingent and subscription dynamic dependencies, a non-contingent, non-subscription dependency is a static dependency. The exemplary producer graph of  FIG. 4A  illustrates a producer graph of static dependencies. 
     Producer Graph Shapes 
     Since a producer in object-oriented programming languages is at least a class, an instance of that class, and a method associated with that instance, a producer graph is class, instance and method centric. As such, a producer graph is a graph representing instances and methods associated with those instances, and thus, producer graphs are at least instance and method centric. In embodiments of the invention in which a producer is at least a class, a method, and an instance, producer graphs are at least class, method, and instance centric. 
     It should be understood that a producer graph may take a variety of different shapes (e.g., a single chain of producers, a tree, etc.). The exemplary producer graph of  FIG. 5B  is a tree with a root node of producer  1 , from which there are two branches—one to each of producer  2  and producer  3 . Where producer  3  is a leaf node, producer  2  has two branches extending from it—one to each of producer  4  and producer  5 . Producer  5  has two branches extending from it—one to each of producer  6  and producer  7 A. The exemplary producer graph of  FIG. 5B  is said to be multilevel, with level  1  including the root node producer  1 , with level  2  including producer  2  and producer  3 , with level  3  including producer  4  and producer  5 , with level  4  including producer  6  and producer  7 A (in  FIG. 5C , level  4  includes producer  7 B, and level  5  includes producer  8 ). In some embodiments, parallelization may be implemented by executing producers on each level in parallel. Execution of producers may begin with the producers in the lowest level, such as level  5  in  FIG. 5C , and then moves up level-by-level. Before start executing producers on a level, the runtime may wait until all producers on a previous lower level are ready, i.e., the outputs of the producers on the previous lower level have been returned. When considering the branch from producer  1  with producer  2 , the first producer of the branch is producer  2  and the last producers of the branch are producer  4 , producer  6 , and producer  7 A in  FIG. 5B . 
     While  FIG. 5B  illustrates a producer graph in which the current set of producers of interest includes a single producer, embodiments of the invention that support more than one current producer of interest would discover and build producer graphs for each. It should be understood that where there are simultaneously multiple producers of interest, the resulting producer graphs may be independent or may intersect. Where producer graphs intersect, embodiments of the invention may be implemented to: 1) duplicate producers to maintain separate producer graphs; or 2) avoid such duplication and maintain intersecting producer graphs. It should also be understood that such intersecting producer graphs may include a producer graph that is a subset of another producer graph. For instance, if producer  5  was included with producer  1  in the current set of producers of interest, then there would be a first producer graph with a root node of producer  5  and a second producer graph with a root node of producer  1 , where the second producer graph includes the first producer graph. If, for instance, producer  7 B was included with producer  1  and producer  5  in the current set of producers of interest, there would be a third producer graph, separate from the first and second producer graph, with a root node of producer  7 B in  FIG. 5B . Further, if the dynamic dependency of producer  5  changed from producer  7 A to producer  7 B ( FIG. 5C ), then the change would result in the second producer graph and the third producer graph remaining (but not the first), with the third producer graph becoming a subset of the second producer graph remaining, and the second producer graph becoming a subset of the first producer graph. As previously stated, while embodiments of the invention may store and manipulate the producer graph(s) as a collection of producers that are linked to each other to form graph(s) (as opposed to a collection of graphs) to facilitate merging and splitting of producer graph(s). By way of example and not limitation, embodiments of the invention which store and manipulate the producer graph(s) as a collection of producers are described herein. 
     Exemplary Execution Flow 
       FIG. 6  is a flow diagram of a logical execution flow of a runtime client and its relationship to a runtime with producer graph oriented programming support according to one embodiment of the invention. In  FIG. 6 , dashed dividing line  600  separates the logical execution flow of a runtime client  610  from the runtime with producer graph oriented programming support  640 . 
     The logical execution flow of the runtime client  610  includes blocks  615 ,  620 ,  625 , and  630 , while the runtime with producer graph oriented support  640  includes blocks  645 ,  650 ,  660 , and optionally  655 . A solid arrowed line represents a direct causal relationship from block  630  to block  660 . In contrast, dotted arrowed lines illustrate a causal relationship from blocks  615  and  625  in the logical execution flow of the runtime client  610  to blocks  645  and  650  in the runtime with producer graph oriented support  640 , respectively; depending on the embodiment of the invention, this causal relationship may be direct or indirect. For example,  FIG. 6  illustrates an optional indirect causation through the use of a command log  665  in a dashed oval on the runtime with producer graph oriented support  640  side of the dashed line  600 . The command log  665  collects commands resulting from blocks  615  and  625  of the logical execution flow of the runtime client  610 ; and the command log  655  is consumed, responsive to block  630 , by processing block  660 . Thus, the command log  665  allows for the delaying of commands in order to collect multiple ones together and batch process them for optimization purposes. Thus, the command log  665  is similar to the override log  396  of  FIG. 3B , and would actually include the override log  396  in some embodiments of the invention. 
     In block  615 , the set of one or more producers of interest are determined as the current set of producers of interest and control passes to block  620 . Responsive to the causal relationship between block  615  and block  645 , block  645  shows that the current set of producers of interest are instantiated and that an attempt is made to discover, build, and resolve (if dynamic dependencies are supported and one or more are discovered in the producer graph) the producer graph(s) for each, including instantiating any instances and producers thereof as necessary, based on the producer dependency declarations in the runtime client  610 . With reference to  FIGS. 3A and 3B , the automated producer graph generation module  340  and  365  are invoked, respectively. 
     In block  620 , it is determined if there are any producer output overrides. If so, control passes to block  625 ; otherwise, control passes to block  630 . 
     In block  625 , one or more producer output overrides are received for a set of one or more producers and control passes to block  630 . Responsive to the causal relationship between block  625  and block  650 , block  650  shows that the current set of overridden producers are instantiated (if not already instantiated in block  645 ), their outputs are modified, and they are tracked. An overridden producer may have already been instantiated because it was already discovered to be part of the producer graph(s) in block  645 . However, an overridden producer may not already be discovered in block  645  because of an unresolved dynamic dependency. As such, this overridden producer is instantiated and overridden with the expectation that it may be added to the producer graph(s) when dynamic dependencies are resolved. Also, as previously indicated, the override log  396  of  FIG. 3B , if implemented, exists between block  625  and block  650  and is part of the command log  665 . Further, the set of overridden producers is tracked in some embodiments of the invention that support incremental execution. While in embodiments of the invention that support the override log  396 /command log  665  the tracking is part of the log, in alternative embodiments of the invention the tracking is separately performed in block  650  with a different mechanism. 
     In block  630 , the producer graph execution module is invoked and control optionally returns to block  615  and/or block  625 . Responsive to the causal relationship between block  630  and block  660 , block  660  shows that the current producer graph(s) are walked and any producers that require execution are executed based on the tracking. Various techniques have been previously discussed for executing the producers of the producer graph and are applicable here. With reference to  FIGS. 3A and 3B , the producer graph execution module  345  and  370  are invoked, respectively. In addition, in embodiments of the invention in which the command log  665  is implemented, the causal relationship includes consuming the command log  665  and performing the processing blocks  645  and  650  prior to block  660 . Further, in embodiments of the invention that support the possibility of unresolved dependencies, control flows from block  660  to block  655  when necessary. 
     In block  655 , an attempt is made to resolve the unresolved dependencies and discover and build the remainder of the producer graph(s), including instantiating any instances and producers thereof. From block  655 , control flows back to block  660 . 
     Exemplary Forms of Producer Dependency Declarations 
       FIGS. 7A-F  illustrates some exemplary forms for producer dependency declarations according to embodiments of the invention. While  FIGS. 7A-F  illustrate embodiments that support argument, field, and sequencing dependencies, it should be understood that different embodiments may support only one or two of the three dependency forms. In the embodiments of the invention shown in  FIGS. 7A-F , a producer dependency declaration is made up of a producer dependency declaration statement, and optionally explicit producer dependency declaration code. A non-shortcut declared producer dependency is one in which explicit producer dependency declaration code is used, whereas a shortcut declared producer dependency is one in which no explicit producer dependency declaration code is used (rather, the runtime does not use producer dependency declaration code and/or implements it on the fly based on information in the producer dependency declaration statement). 
     Different embodiments of the invention may use different syntaxes for declaring producer dependencies. For example, different embodiments of the invention may include different syntaxes for use in producer dependency declaration statements that strongly constrain, weakly constrain, and/or do not constrain the type of producer dependency that may be created. A strongly constrained producer dependency is one for which a syntax is used in the producer dependency declaration statement that substantially limits the type of producer dependency that may be created; A weakly constrained producer dependency is one for which a syntax is used in the producer dependency declaration statement that is less limiting of the type of producer dependency that may be created; and an unconstrained producer dependency is one for which a syntax is used in the producer dependency declaration statement that does not limit the type of producer dependency that may be created. 
     By way of example, and not limitation, embodiments of the invention described below that include the following: 1) a syntax for a strongly constrained producer dependency for arguments (ArgumentDependency=strongly constrained downwardly declared argument [static or dynamic, and if dynamic, contingent and/or absorbing subscription] dependency); 2) a syntax for a strongly constrained producer dependency for fields (FieldDependency=Strongly constrained downwardly declared field [static or dynamic, and if dynamic, contingent and/or absorbing subscription] dependency); 3) a syntax for a strongly constrained producer dependency for sequencing dependencies (SequencingDependency=Strongly constrained downwardly declared sequencing [static or dynamic, and if dynamic, contingent and/or sticky subscription] dependency); 4) a syntax for a weakly constrained upwardly declared producer dependency for argument, field, or sequencing dependencies (UpwardDependency=Weakly constrained upwardly declared field, argument, or sequencing [static or dynamic, and if dynamic, contingent] dependency); and 5) a syntax for a weakly constrained producer dependency (WeaklyConstrainedDependency=either a) downwardly declared sequencing only [static or dynamic, and if dynamic, contingent and/or sticky subscription] dependency; or b) upwardly declared [argument, field, or sequencing] [static or dynamic, and if dynamic, contingent] dependency). It should be understood that while some embodiments of the invention support a syntax for the producer dependency declaration statement that distinguishes downwardly declared argument dependencies, downwardly declared field dependencies, upwardly declared dependencies (that can return upwardly declared argument, field, or sequencing dependencies), and weakly constrained dependencies (that can return downwardly declared sequencing dependencies, upwardly declared argument, field, or sequencing dependencies), alternative embodiments of the invention may adopt a different syntax (e.g., have a syntax that has all dependencies be unconstrained dependencies with dependency determination producers that can return any supported dependencies (downwardly and upwardly declared argument, field, and sequencing dependencies); have a syntax distinguish all supported dependencies; have a syntax that distinguishes downwardly and upwardly declared argument and field dependencies and that distinguishes a weakly constrained dependency that can only return upwardly and downwardly declared sequencing dependencies; a syntax that distinguishes downwardly declared argument and field dependencies and that distinguishes upwardly declared dependencies that can return only upwardly declared sequencing dependencies; a syntax that distinguishes downwardly declared argument, field, and sequencing dependencies (sticky subscriptions and upwardly declared dependencies are not supported); etc). 
     It should be understood that the syntax of the producer dependency declaration statement does not necessarily equate to the producer dependency (e.g., the link) created in the producer graph (e.g., ArgumentDependency creates an argument dependency; but an UpwardDependency may create an argument, field, or sequencing dependency). As such, where appropriate for understanding, a space between a qualifier (e.g., argument, field, or sequencing) and the word “dependency” is used to refer to the dependency created by the runtime, while lack of a space is used to refer to the syntax. 
       FIG. 7A  illustrates pseudo code of a producer dependency declaration for a method using shortcut declared dependencies according to one embodiment of the invention; while  FIG. 7B  is a block diagram of exemplary producers according to one embodiment of the invention.  FIG. 7A  shows: 1) a producer dependency declaration statement  705  including ArgumentDependencies  1 -N, FieldDependencies  1 -M, SequencingDependencies  1 -L, UpwardDependencies  1 -P, and WeaklyConstrainedDependencies  1 -Q; and 2) a method alpha  710  having arguments  1 -N from the producer dependency declaration statement  705 . In one embodiment of the invention, the arguments of a producer dependency declaration statement are numbered to provide an argument ID for each for tracking purposes.  FIG. 7B  shows a producer  720  having child dependencies to the following: 1) producer  725  for argument ID  1 ; 2) producer  730  for argument ID N; 3) producers  740 - 745  for field dependencies  1 -M; 4) producers  746 - 747  for SequencingDependencies  1 -L; and 5) producer  748 - 749  for UpwardDependencies  1 -P (note, WeaklyConstrainedDependencies  1 .Q are not shown, but will be described in greater detail with reference to  FIG. 7G ). Thus, the arguments of the producer dependency declaration statement  705  correspond to the arguments of the method alpha  710 , and the argument IDs of the arguments in the producer dependency declaration statement  705  are tracked with regard to the child producers they identify. 
       FIG. 7C  illustrates pseudo code of a producer dependency declaration for a method using a non-shortcut declared dependency, and illustrates a block diagram of exemplary producers according to one embodiment of the invention.  FIG. 7C  shows the producer dependency declaration statement  705  and the method alpha  710  of  FIG. 7A , as well as the producers  720  and  725  from  FIG. 7B . In addition,  FIG. 7C  includes producer dependency declaration code  715  associated with Argument Dependency  1 . During run time, the runtime accesses and executes the producer dependency declaration code  715  responsive to Argument Dependency  1  of the producer dependency declaration statement  705 . Execution of the producer dependency declaration code  715  returns the producer  725  as the producer dependency for Argument Dependency  1 . Thus,  FIG. 7C  illustrates embodiments of the invention in which producer dependency declaration code  715  may be part of a method (other than method alpha  710 ), but is not part of a producer. 
       FIG. 7D  illustrates pseudo code of a producer dependency declaration for a method using a non-shortcut declared dependency according to one embodiment of the invention; while  FIG. 7E  is a block diagram of exemplary producers according to one embodiment of the invention.  FIG. 7D  shows the producer dependency declaration statement  705  and the method alpha  710  of  FIG. 7A , while  FIG. 7E  shows the producers  720  and  725  from  FIG. 7B . In addition,  FIG. 7D  includes: 1) a producer dependency declaration statement  750 ; and 2) a method beta  755  including producer dependency declaration code  760 .  FIG. 7D  also shows that argument dependency  1  of the producer dependency declaration statement  705  identifies a producer (shown in  FIG. 7E  as producer  765 ) based on the method beta  755  that will return the dependency for argument dependency  1 . During run time, the runtime, responsive to argument dependency  1  of the producer dependency declaration statement  705 , executes the producer  765  to return identification that the producer dependency for argument dependency  1  is producer  725 . As such, producer  765  is referred to as a dependency determination producer (its output is producer dependency—and thus, is returned using a class/instance that is monitored for special treatment (manipulation of the producer graph(s)) by the runtime with producer graph oriented programming support), whereas producer  725  is referred to as a standard producer (its output, if any, is not directly processed by the runtime to manipulate a producer graph; but its output, if any, may be consumed by a parent producer (be it a dependency determination producer or another standard producer) and/or provided as the output of the producer graph (if the standard producer is a producer of interest, and thus a root node). 
     Thus,  FIGS. 7D-E  illustrate embodiments of the invention in which producer dependency declaration code  715  is part of another producer—referred to as a dependency determination producer. While in  FIGS. 7D-E  the object-oriented source code includes explicit producer dependency declaration code in methods from which dependency determination producers are instantiated at run time by the runtime for non-shortcut declared dependencies, alternative embodiments of the invention additionally or instead implement the runtime to include generic producer dependency declaration code that it invokes as one or more generic dependency determination producers on the fly for shortcut declared dependencies. Also, while  FIGS. 7C-E  are illustrated with reference to ArgumentDependencies, the techniques illustrated are applicable to the other types of downwardly declared dependencies. Further,  FIGS. 7F-G  illustrate the use of a dependency determination producer for an UpwardDependency and a WeaklyConstrainedDependency. 
       FIG. 7F  is a block diagram of an exemplary dependency through use of an UpwardDependency with a dependency determination producer according to one embodiment of the invention.  FIG. 7F  shows the producer  720  having sequencing producer dependency to a dependency determination producer  772 . The dependency determination producer may return a non-subscription upwardly declared argument, field, or sequencing dependency of the parent producer  748  on the producer  720 . Further, such a dependency determination producer may implement a dynamic dependency (e.g., a contingent dependency that selects between the above depending on data values, including between different argument IDs, as described later herein). While some embodiments of the invention support all of these possibilities, alternative embodiments of the invention support only a subset (e.g., only non-subscription upwardly declared sequencing dependencies). 
       FIG. 7G  is a block diagram of possible exemplary dependencies through use of a WeaklyConstrainedDependency with a dependency determination producer according to one embodiment of the invention.  FIG. 7G  shows the producer  720  having sequencing producer dependency to a dependency determination producer  775 . In some embodiments of the invention, the dependency determination producer may return any of the following: 1) a non-subscription downwardly declared sequencing dependency on a child producer  780 ; 2) a non-subscription upwardly declared argument, field, or sequencing dependency of a parent producer  785  on the producer  720 ; and 3) a sticky subscription (described later herein). Further, such a dependency determination producer may implement a dynamic dependency (e.g., a contingent dependency that selects between the above depending on data values, including between different argument IDs, as described later herein). While some embodiments of the invention support all of these possibilities, alternative embodiments of the invention support only a subset (e.g., only non-subscription upwardly declared sequencing dependencies). 
     As previously indicated, sequencing dependencies may be used for a variety of purposes, including ensuring the order of execution between producers that modify data in a manner of which the runtime is not aware and producers that consume that data (a child producer may write its outputs in a way that requires the method of the parent producer to include code to access that output (e.g., a method that impacts the environment by affecting an output that is not the regular producer output and, as such, that is not detected by the runtime—such as a method that sets a global variable, that sets a field in an instance which is not the producer output, that impacts an external data source, etc.)), etc. Affecting sources (such as global variables or external data sources) that the runtime is not aware of and reading from these sources is a feature that should be avoided in producers where parallelization capabilities are required. 
     Different embodiments may support one or more ways for declaring producer dependencies with respect to property producers. Specifically, in some embodiments of the invention, producers that read a field should be dependent on the get property producer, while the get property producer should be dependent on any producers that set the field for which that get property method is responsible. One technique of handling this situation that may be used in embodiments of the invention that support sequencing producer dependencies is to provide, for a get property method, a producer dependency declaration statement that creates sequencing producer dependencies on every method that sets the field for which that get property method is responsible (e.g., with respect to  FIG. 7G , where the producer  780  is a producer that sets a field and the producer  720  is the get property producer responsible for that field, the dependency determination producer  775  would be written to return a downwardly declared sequencing dependency of the producer  720  on the producer  780 ). A second technique of handling this situation that may be used in embodiments of the invention that support both sequencing producer dependencies and upwardly declared producer dependencies is to include, in the producer dependency declaration statement/code for any method that sets a field, an upwardly declared sequencing producer dependency (e.g., using an UpwardDependency or WeaklyConstrainedDependency) on the get method responsible for that field (e.g., with respect to  FIG. 7G , where the producer  720  is a producer that sets a field and the producer  785  is the get property producer responsible for that field, the dependency determination producer  775  would written to return an upwardly declared sequencing dependency of the parent producer  785  on the producer  720 ). This second technique allows the programmer of the method that sets the field to be responsible for providing a producer dependency to the appropriate get method, as opposed to requiring that programmer to go to the get method and modify its producer dependency declaration statement/code. 
     When using sequencing dependencies, when a given producer relies on a given variable, that variable should not be modified by more than one of that producer&#39;s descendant producers in a given execution of the producer graph(s) (It should be noted that through contingent dependencies (described later herein), different descendant producers may modify that variable during different executions of the current producer graph(s)). For example, a get property producer should only depend on one other producer that sets the filed for which the get property producer is responsible in a given execution of the current producer graph(s). 
     It should be understood that different embodiments of the invention may implement one or more of the embodiments of the invention shown in  FIGS. 7A-F . For example, one embodiment of the invention supports shortcut and non-shortcut declared dependencies, both using dependency determination producers; specifically, in this embodiment of the invention: 1) the object-oriented source code includes explicit producer dependency declaration code in methods from which dependency determination producers are instantiated at run time by the runtime for non-shortcut declared dependencies; 2) the runtime includes generic producer dependency declaration code that it invokes as one or more generic dependency determination producers on the fly for shortcut declared, contingent dependencies (describer later herein); and 3) the runtime includes support to directly link shortcut declared, non-contingent producer dependencies (describer later herein). 
     As another example, one embodiment of the invention supports non-shortcut and shortcut producer dependencies using dependency determination producers; specifically, in this embodiment of the invention: 1) the object-oriented source code includes explicit producer dependency declaration code in methods from which dependency determination producer are instantiated at run time by the runtime for non-shortcut declared dependencies; and 2) the runtime includes generic dependency determination code that it invokes as one or more generic dependency determination producers on the fly for shortcut declared dependencies (regardless of type). This later embodiment allows for consistent treatment of producer dependencies, and thus, simplifies the runtime. 
     In addition, while in one embodiment of the invention the producer dependency declaration statement for a method is located just above that method in the object-oriented source code, in alternative embodiments of the invention it is located elsewhere (e.g., the producer dependency declaration statements for all the methods for a class are grouped together within the class, the producer dependency declaration statements for all the methods in all of the classes are grouped together as a separate data table, etc.). Also, while in one embodiment of the invention producer dependency declaration code is separate from the producer dependency declaration statements, in alternative embodiments of the invention they are combined (e.g., the producer dependency declaration code is within the parentheses of the producer dependency declaration statement, the producer dependency declaration code is placed directly beneath the producer dependency declaration statement and is treated by the runtime as a single unit, etc.). 
       FIGS. 7H-I  illustrate the distinction between different subgraphs that may exist in a producer graph due to dependency determination producers.  FIG. 7H  illustrates exemplary producer graphs of standard producers according to one embodiment of the invention. Specifically,  FIG. 7H  shows a producer graph with root node  51 , a producer graph with root node S 5 , and a producer graph with root node S 11 . The standard producer  51  has as children standard producers S 2 , S 3 , and S 4 ; standard producers S 2  and S 3  have as children standard producers S 7  and S 8 ; standard producer S 5  has as children standard producers S 4  and S 6 ; and standard producer S 11  has as children standard producers S 6  and S 10 . The exemplary producer graphs of  FIG. 7H  may be discovered, built, and revolved using any number of producer dependencies and dependency determination producers.  FIG. 7I  illustrates one example of producer dependencies and dependency determination producers for discovering, resolving, and building the producer graph of  FIG. 7H . Specifically,  FIG. 7I  shows the graphs of  FIG. 7H  being subgraphs of a larger set of producer graphs. In other words, the producer graphs of  FIG. 7I  include the graphs of  FIG. 7H  (referred to as the “target subgraphs” and illustrated using solid arrowed lines and solid ovals) and graphs that assist in the discover, resolution, and building of the target subgraphs (referred to as “decision subgraphs and illustrated used dashed arrowed lines and dashed ovals). The decision subgraphs in  FIG. 7H  include dependency determination producers (DDPs)  1 - 11  and standard producers S 9 - 10 . In  FIG. 7H , S 1  is shown as being dependent on DDPs  1 - 3 , which respectively return downwardly declared producer dependencies of S 1  on S 2 , S 3 , and S 4 ; S 4  is shown as being dependent on DDP 4 , which returns an upwardly declared producer dependency of S 5  on S 4 ; S 5  is shown as being dependent on DDP 5 , which returns a downwardly declared producer dependency of S 5  on S 6 ; S 3  is shown as being dependent on DDP 6 , which in turn is dependent on DDP 8 , which returns a downwardly declared producer dependency of DDP 6  on S 9  and S 10 , which causes DDP 6  to return a downwardly declared dependency of S 3  on S 7 ; S 3  is shown as being dependent on DDP 7 , which returns a downwardly declared producer dependency of S 3  on S 8 ; S 8  is shown as being dependent on DDP 9 , which returns a sticky subscription for which S 6  is a trigger producer and S 11  is the created parent (thus, the producer dependency of S 11  on S 6 ); S 2  is shown as being dependent on DDP 10 , which returns a collection of downwardly declared producer dependency of S 2  on S 7  and S 8 ; and S 11  is shown as being dependent on DDP 11 , which returns a downwardly declared producer dependency of S 11  on S 10 . It should be understood that a standard producer may be both part of a target subgraph and a decision subgraph (e.g., see S 10 ). It is worth noting that the target subgraphs are data driven in the sense that data flows from one standard producer to another standard producer up the graph. 
     Exemplary Programming and Execution Framework 
       FIG. 8A  is a block diagram illustrating a first exemplary framework within which applications are provided to end users according to one embodiment of the invention. The framework shown in  FIG. 8A  includes three basic divisions. The first division includes the creation of the runtime with producer graph oriented programming support  810 . This first division is performed by programmers with highly advanced programming skills. When working in this division, programmers are referred to as runtime programmers. When creating a runtime with producer graph oriented programming support, the runtime programmers include support for producer graphs, as well as support for executing the various types of commands used in transformation code, instantiation code, and data preparation code. 
     The second division includes the creation of object-oriented application source code  820  to be executed by the runtime. The object-oriented application source code  820  includes two basic divisions: 1) class definitions that include the business logic expressed in methods with producer dependency declarations  822  (this may optionally include other functionality, such as a graphical user interface—in which case, the graphical user interface is written using producers and producer dependency declarations); and 2) class definitions that include client code expressed in methods  824 , including instantiation code (class, instances, and producer(s) of interest, to cause generation of the producer graph(s))  824 A, data preparation code  824 B (e.g., set commands, such as set commands that trigger the overriding of producer outputs), global execute commands  824 C to cause execution of the producer graph(s) (e.g., execute and get commands), and any required graphical user interface  824 D (not included in  822 ). The producer dependency declarations are used to define the ties between producers during the definition of the classes that include the business logic, rather than after instances of those classes are created. The object-oriented source code  820  is hard coded class, instance, and methods that are compiled and executed. 
     While in one embodiment of the invention a global execute command is implemented, execution of which causes the attempted execution of all producer graph(s) currently in the producer graph(s) structure  380 , alternative embodiments of the invention alternatively or also implement a graph specific execute command that requires identification of a given graph of the current producer graph(s) that is to be executed. Further, the global execute command may be explicit (e.g., set, set, set, execute, get, get) or implicit depending on the implementation of the runtime. For example, an implicit global execute command could be: 1) triggered by the first get command on a producer of interest (e.g., set, set, set, get (implicit execute), get); 2) trigger by each data manipulation (set (implicit execute), set (implicit execute), set (implicit execute), get, get); etc. 
     The second division is again performed by programmers with advanced programming skills, as well as an understanding of the business objectives of the application. When working in this division, programmers are referred to as application programmers. As part of this, if the application requires a graphical user interface, the application programmers also design and code the graphical user interface for the specific application; and thus are also referred to as application designers. 
     The third division includes the use of application programs being run by the runtime. The third division is performed by end users that need not have any programming skills. The application program may be distributed in a variety of ways (e.g., as source code; a transformation of source code, such as byte code; as binary, etc.). In addition, the application program may be distributed for stand alone use  830  (in which case, the entire application program (and runtime if not already present) is provided to a computer system) and/or client/server use. In one embodiment of the invention, a client/server distribution includes distributing the class definitions that include the business logic expressed in methods with producer dependency declarations  822  (and runtime if not already present) for server use  832  and the class definitions that include client code expressed in methods  824  (and runtime if not already present) for client use  834 , where the client use  834  on a computer system causes communication with the server use  832  on a server system. 
       FIG. 8A  also shows an optional configurable interactive producer output layout graphical user interface module  840  being provided for the standalone use  830  and the client use  834 . The object-oriented source code  820  would be run by the runtime to generate the producer graph(s), and the configurable interactive producer output layout graphical user interface module  840  allows for graphically displaying outputs from and interacting with the producer graphs. Specifically, the configurable interactive producer output layout graphical user interface module  840  includes: 1) a configuration and mapping graphical user interface module  844  to allow for the configuration of the layout and mapping of selected producer outputs (e.g., areas of the screen to be used, how the data is to be displayed, etc.); and 2) a rendering and interaction graphical user interface module  846  to render the configured layout and to allow for the overriding of producer outputs (which results in the updating of the producer graphs through a global execute command). It should be understood that the configurable interactive producer output layout graphical user interface module  840  may or may not be created by the same entity that writes the runtime  810 . 
       FIG. 8B  is a block diagram illustrating a second exemplary framework within which applications are provided to end users according to one embodiment of the invention.  FIG. 8B  is identical to  FIG. 8A , with the following exceptions: 1) the stand alone used  830  is not present; 2) the object oriented source code  820  is provided to server use  832 , while the client code  824  is not provided to client use  834 ; 3) the configurable interactive producer output layout graphical user interface module  840  is provided to server use  832  and not client use  834 ; and 4) a generic configurable interactive producer output layout client interface  885  is provided to client use  834 . The configurable interactive producer output layout client interface  885  is used to interface with the configurable interactive producer output layout graphical user interface module  840 . 
     Regardless of the framework used, in one embodiment of the invention the producer graph oriented programming framework offers the ability to interface with programs not written with producer dependency declarations. This ability to interface with programs not written with producer dependency declarations includes: 1) a caller part (such as a graphical user interface not written according to producer graph oriented programming); and 2) a called part (such as an external data source not written according to producer graph oriented programming). The caller part may, through client code, issues producer graph oriented programming commands. The called part is implemented as part of producers that wrap the called part (referred to as “wrapping producers”). Executing the called part (such as reading data from a data source or subscribing to changes of data in an external data source) may in turn trigger instance modifications. These changes may occur by calling the property set methods in the code of the wrapping producers. Get property producers (getters) are caused to have dependencies on these wrapping producers, in order to make sure that instance modifications triggered by the changes occurring in an external data source are properly propagated through the producer graph. As previously described, different embodiments may support one or more ways for declaring producer dependencies with respect to property producers. For example, in some embodiments of the invention that support sequencing producer dependencies, SequencingDependencies may be used for declaring non-subscription downwardly declared sequencing producer dependencies on the wrapping producers. As yet another example, in some embodiments of the invention that support sequencing producer dependencies and non-subscription upwardly declared producer dependencies, UpwardDependencies and/or WeaklyConstrainedDependencies may be may be placed in the producer dependency declaration of the wrapping producers to create non-subscription upwardly declared sequencing producer dependencies for the property producers. 
       FIGS. 8C-F  illustrate exemplary screenshots and usage of the configurable interactive producer output layout graphical user interface module  840  according to one embodiment of the invention. While embodiments of the invention will be described with reference to the configurable interactive producer output layout graphical user interface module  840  providing for the configuration, mapping, and interaction with selected outputs of the current producers graph(s) in the form of a spreadsheet, alternative embodiments of the invention may be implemented to additionally or alternatively provide support for another form. Further, while exemplary ways of performing the configuration, mapping, and interaction in the form of a spreadsheet is described according to some embodiments, other embodiments of the invention may perform these operations another way, with different interface, and/or with a different screen layout. Further, the spreadsheet may support any of the known functionalities associated with spreadsheets (e.g., color selection, font selection, bar/pie/line charts, pivot tables, saving layouts, loading layouts, etc.). 
       FIGS. 8C-D  illustrate exemplary screenshots and usage of free cell selection according to one embodiment of the invention, while  FIGS. 8E-F  illustrate exemplary screenshots and usage of table creation according to one embodiment of the invention. Each of  FIGS. 8C-F  include a menu bar  850  along the top of the screen, a list of classes (with their get property methods)  852  of the producers in the current producer graph and their outputs down the left side of the screen, and a configuration and mapping viewer  854  filling the remainder of the screen with a spreadsheet like layout. In addition,  FIGS. 8C-F  also show the following exemplary list of classes with their get property methods in the list  852 : 1) the class PERSON; 2) the get property methods of the class person including FIRSTNAME (e.g., string), LASTNAME (e.g., string), GENDER (e.g., string), HOMEADDRESS (instance of the class ADDRESS), PROFESSIONALADDRESS (instance of the class ADDRESS), DATEOFBIRTH (e.g., date), and AGE (e.g., integer); 3) the class ADDRESS; and 4) the get property methods of the class ADDRESS including CITY (e.g., string), STATE (e.g., string), ZIPCODE (e.g., string). As such, the current producer graph includes producers of the classes PERSON and ADDRESS, as well as producers whose outputs are of classes PERSON and ADDRESS. It is also worth nothing that the get property method AGE calculates an age based on the output of the get property method DATEOFBIRTH; as such, a producer instantiated from the get property method AGE will be dependent on a producer instantiated from the get property method DATEOFBIRTH. 
       FIGS. 8C-D  show the following free text entered in consecutive cells of the first column of the viewer: CUSTOMER, FIRST NAME, LAST NAME, DATE OF BIRTH, and AGE; while  FIGS. 8E-F  show the following: 1) free text entered in the first row of the viewer—CUSTOMER LIST; and 2) free text entered in consecutive cells of the second row of the viewer FIRST NAME, LAST NAME, DATE OF BIRTH, AND AGE. 
       FIG. 8C  illustrates an exemplary screenshot and usage of free cell selection with the configurable interactive producer output layout graphical user interface module  840  according to one embodiment of the invention.  FIG. 8C  shows a set of mappings  856  of the class PERSON and selected get property methods of the class PERSON to different cells of the viewer. Specifically, the class PERSON is mapped to the cell to the right of the free text CUSTOMER. As part of this action, some embodiments of the invention prompt the user to select from one of a number of supported filters (show as filter selection  858 ) (e.g., drop down list, form scrolling arrows, etc.). These filters enable the selection of one or more instance keys of producers of the selected class, or one or more instance keys of the producers whose output class is the selected class. While some embodiments of the invention support a number of filters, other embodiments of the invention default to one (and allow the user to chose whether to select a different one) or support only one and do not need to perform filter selection  858 . The mappings  856  also show that the get property methods FIRSTNAME, LASTNAME, DATEOFBIRTH, and AGE of the class PERSON are respectively mapped to the cells adjacent to the cells with corresponding free text. Such a mapping may be performed with any number of well known techniques, including drag and drop, typing in a GUI field, etc. 
       FIG. 8D  illustrates another exemplary screenshot and usage of free cell selection with the configurable interactive producer output layout graphical user interface module  840  according to one embodiment of the invention.  FIG. 8D  shows that the cell to which the class PERSON was mapped to allow for instance selection  854 . Specifically, based on the filter used for this cell, the user is given the opportunity to select an instance of the class PERSON from a list including the instance keys (s) of the producers of the class PERSON, and the instance keys of the producers producing the class PERSON. The selection of an instance of the class PERSON (or the existence of a single instance) results the automatic population of the cells, to which the get property methods of the class PERSON were mapped, with the outputs of the corresponding get property methods of that instance. This populating of the table based on the instances of the class PERSON is labeled  858 . In the example of  FIG. 8D , the cells to which the get property methods FIRSTNAME, LASTNAME, DATEOFBIRTH, and AGE of the class PERSON were mapped being respectively populated with JOHN, SMITH, Jul. 20, 1990, and 16. 
       FIG. 8D  also shows that cells of the viewer to which get property methods have been mapped may be overridden. By way of example,  FIG. 8D  shows that if the cell to which the get property method DATEOFBIRTH is mapped is overridden, then it will cause the overriding of the output of the producer whose output is currently populating that cell, invocation of a global execute command (which would result in a reexecution of the producer whose output is currently populating the cell to which the get property method AGE is mapped), and any necessary updating of the display. 
       FIG. 8E  illustrates an exemplary screenshot and usage of table creation with the configurable interactive producer output layout graphical user interface module  840  according to one embodiment of the invention.  FIG. 8E  shows a zone and orientation selection  864  operation is performed to identify a three row vertical table directly under the cells with free text FIRST NAME, LAST NAME, DATE OF BIRTH, AND AGE (illustrated with a thick dashed line around these cells). Different embodiments of the invention may support the user performing this operation any number of ways (including: 1) selection of an area with an input device like a mouse; and 2) selection between a vertical, horizontal, or pivot table with an interface like a popup menu—assuming multiple orientations are supported).  FIG. 8E  also shows a set of mappings  866  of selected get property methods of the class PERSON to different cells of the viewer. Specifically, the mappings  866  show that the get property methods FIRSTNAME, LASTNAME, DATEOFBIRTH, and AGE of the class PERSON are respectively mapped to the cells directly beneath the cells with corresponding free text. 
       FIG. 8F  illustrates another exemplary screenshot and usage of table creation with the configurable interactive producer output layout graphical user interface module  840  according to one embodiment of the invention. The mappings  866  results in the automatic population of the columns of the table, to which the get property methods of the class PERSON were mapped, with the outputs of the corresponding get property methods of the instances of that class. This populating of the table based on the instances of the class PERSON is labeled  868 . In the example of  FIG. 8D , the columns to which the get property methods FIRSTNAME, LASTNAME, DATEOFBIRTH, and AGE of the class PERSON were mapped being populated with the following rows of data: 1) STEVE, COLLINS, Jul. 20, 1990, and 16; 2) JENNIFER, ADAMS, Jul. 20, 1990, and 16; and 3) JOHN, SMITH, Jul. 20, 1985, and 21. 
     As in  FIG. 8D ,  FIG. 8F  shows that cells of the viewer to which get property methods have been mapped may be overridden. By way of example,  FIG. 8F  shows that if the cell of the second row of the column to which the get property method DATEOFBIRTH is mapped is overridden, then it will cause the overriding of the output of the producer whose output is currently populating that cell, invocation of a global execute command (which would result in a reexecution of the producer whose output is currently populating the cell to which the get property method AGE is mapped), and any necessary updating of the display. 
       FIGS. 8C-F  illustrate exemplary screens generated by the configuration and mapping graphical user interface module  842 . The screens generated by the rendering and interactive graphical user interface module  846  are the same, with the exception that the list of classes (with their get property methods)  852  the configuration and mapping viewer  854  are replaced by a rendering and interactive viewer (not shown) that contains the same image as the configuration and mapping viewer  854  displayed (the difference being the mapping feature is no longer available). 
     Exemplary Runtime Distribution Schemes 
       FIGS. 9A-C  illustrate various schemes for distributing a runtime with producer graph oriented programming support. It should be understood that these distribution schemes are exemplary, and thus other schemes are within the scope of the invention. 
       FIG. 9A  is a block diagram illustrating a first scheme for distributing a runtime with producer graph oriented programming support according to one embodiment of the invention. In  FIG. 9A , object-oriented source code  905  (which would include producer dependency declarations) is shown on top of a runtime with producer graph oriented programming support  910 , which is on top of a runtime with class loading, dynamic class instantiation, dynamic single method invocation, and class/method introspection  915 , which is on top of an operating system  920 . In  FIG. 9A , the runtime  910  works with the runtime  915 . While any number of mechanisms may be used to allow runtime  910  to work with runtime  915 , a metadata facility is described by way of example. A metadata facility allows additional information to be added to source code, which information is used by development tools. For example, the Metadata Facility for Java specification defines an API for annotating fields, methods, and classes as having particular attributes that indicate they should be processed in special ways by development tools, deployment tools, or run-time libraries (Java Specification Request 175). In this example, a programmer programming the object-oriented source code  905  would add annotations to methods in the form of the producer dependency declarations. Since these annotations are handed off by the runtime  915  to the runtime  910 , the runtime  910  dictates the syntax of the producer dependency declarations. In  FIG. 9A , the runtimes  910  and  915  may be developed and/or distributed by different organizations. 
       FIG. 9B  is a block diagram illustrating a second scheme for distributing a runtime with producer graph oriented programming support according to one embodiment of the invention. In  FIG. 9B , object-oriented source code  925  (which would include producer dependency declarations) is shown on top of a runtime (with class loading, dynamic class instantiation, dynamic single method invocation, and class/method introspection, as well as producer graph oriented programming support)  930 , which is on top of an operating system  935 . In comparison to  FIG. 9A , the runtime  910  and  915  have been combined into a single runtime  930 . As a result of this combination, the runtime  930  dictates the syntax of the producer dependency declarations. Thus, a programmer programming the object-oriented source code  925  would add the producer dependency declarations in the required syntax. 
       FIG. 9C  is a block diagram illustrating a third scheme for distributing a runtime with producer graph oriented programming support according to one embodiment of the invention. In  FIG. 9C , object-oriented source code  940  (which would include producer dependency declarations) is shown on top of an operating system runtime (with class loading, dynamic class instantiation, dynamic single method invocation, and class/method introspection, as well as producer graph oriented programming support)  945 . In comparison to  FIG. 9B , the runtime  920  and operating system  935  have been combined into a single entity. As a result of this combination, the operating system runtime  945  dictates the syntax of the producer dependency declarations. Thus, a programmer programming the object-oriented source code  940  would add the producer dependency declarations in the required syntax. 
     While embodiments are described in which the runtime has class loading, dynamic class instantiation, dynamic single method invocation, and class/method introspection, alternative embodiments may include more or less features (e.g., instance cloning, dynamic proxies, primitive type conversions, etc.). 
     Exemplary Advantages 
     In one embodiment of the invention, producer dependencies are declared for methods as a way to specify method invocation sequencing using the appropriate instances (where the appropriate instances include the instances to use as arguments, the instances to be used by instance methods, and the meta class instances used by class methods) without using manual invocation sequencing code. Effectively, the work of generating some or all of manual invocation sequencing code is replaced with: 1) work done by the application programmer to write the producer dependency declarations; and 2) work done by the runtime to discover and build the producer graph(s) and execute the producers of those producer graph(s). In other words, the logic that was previously contained in the manual invocation sequencing code is discoverable by the runtime during run time based on the producer dependency declarations. Thus, the producer dependency declarations inform the runtime what methods of what instances with what arguments to execute, and when for synchronization purposes. Although the effort to write the runtime is relatively great, it needs only be written once in that it can be used to execute any object-oriented applications written for the runtime; in contrast, for a typical application, the effort to write the producer dependency declarations is relatively low in comparison to writing manual invocation sequencing code. 
     Reducing Programming Mistakes 
     Producer graph oriented programming typically reduces the costs associated with the debugging and/or performance tuning of the manual invocation sequencing code. This is true for at least the reason that the infrastructure of an application program is conceptually a set of non-formalized graphs of transformation methods of objects (the output of one method of an object is the input to another, and so on) that operate on specific inputs. The producer dependency declarations and the runtime with producer graph oriented programming support formalizes these graphs as producer graphs. Thus, for each opportunity for data to change, the application programmer need not consider its effect and write manual invocation sequencing code to cause the appropriate transformation methods of the appropriate instances to be invoked in the appropriate order with the appropriate inputs. In other words, for each opportunity for data to change, an application programmer need not consider which graphs are affected, as well as which transformation methods of instances within those graphs are affected. Rather, the automated producer graph generation module discovers and builds the producer graphs and the producer graph execution module reexecutes the producer graphs as needed to reflect changes in the data. This automation helps application programmers avoid mistakes such as: 1) invoking the appropriate transformation methods of the appropriate instances in the wrong order; 2) forgetting to include commands to cause the one or more required transformation methods of instances in a graph to be invoked responsive to some data being changed; 3) including commands to cause unnecessary transformation methods of instances to be invoked responsive to some data being changed (e.g., including commands to invoke transformation methods of instances that are not part of a graph affected by the change in data; including commands to invoke transformation methods of instances that are part of a graph affected by the change in the data, but are not themselves affected; etc.). 
     Synchronization 
     As previously described, the caching of producer outputs during execution allows for synchronization. Thus, in terms of comparison to the observer pattern, the producer dependency declarations notify a runtime with producer graph oriented programming support of the dependencies, and the runtime determines what producers and when to call back. 
     Ability to Fully Explain any Result 
     In one embodiment of the invention, a drilling/viewing module (not shown) is included as part of the runtime. The drilling/viewing module provides a graphical user interface which, through interaction by an end user, allows for drilling down into the producer graph (walking down a producer graph from the root node) to view the outputs of the various producers of the producer graph. This allows an end user to see the various outputs that contributed to the output of the producer of interest, including the data values and dependencies (returned by dependency determination producers). Further, in one embodiment of the invention, this drilling/viewing module provides the ability for the end user to view the code inside the methods of the producers, the values of the instances of the producers, and/or the content of the classes of the producers. 
     Thus, the drilling/viewing module provides for a variety of post processing activities, including debugging, explanation of outputs, etc. 
     Exemplary Practical Application/Technical Affect/Industrial Applicability 
     There are a variety of exemplary practical applications of the different aspects and embodiments of the invention. For example, the runtime, as part of executing application programs, causes the retrieval of information from a machine storage media (e.g., accessing the object-oriented source code, including the producer dependency declarations), the storage of information to a machine storage media (e.g., storing data structures like the producer graph(s) structure, etc.), the operation of hardware processing resources, the provision of the outputs of the producer(s) of interest (e.g., through a graphical user interface, storage to machine storage media, transmission, etc.), etc. In one sense, preprocessing activity includes the writing of such an application program and/or the provision of data (which data may represent any number of physical and/or practical items, such as financial values, geographical values, meteorological values, actuarial values, statistical values, physical measures, machine state values, etc.), while post processing activity includes the provision of results (which results may represent any number of physical and or practical items, such as financial analysis, geographical analysis, meteorological analysis, actuarial analysis, statistical analysis, industrial measures, machine control information, etc.). By way of specific example, post processing activity may be provided by: 1) the producer graph viewer module  1062  of  FIG. 10  for graphically displaying a representation of the current producer graph(s) generated by the runtime; and/or 2) the configurable interactive producer output layout graphical user interface module  840  (see also, configurable interactive producer output layout graphical user interface module  1085  of  FIG. 10 ) for graphically displaying outputs from and interacting with the producer graphs. 
     As another example, the application program with producer dependency declarations itself, when executed by the runtime, represents the physical/practical items and causes the operations described above. By way of specific example, these producer dependency declarations cause data structures to be formed in machine storage media responsive to their execution by the runtime. Also, the producer dependency declarations are stored and retrieved from machine storage media along with the application program. Further, these producer dependency declarations represent relationships between producers, while producers represent operations to be performed (methods) and instances. The instances in object-oriented programming may be used to represent physical and/or practical items, while the producers represent operations to be performed on these representations. 
     By way of another example, a set of one or more application programs and the runtime implement cross-asset risk management software covering foreign exchange, equity, interest rate, credit, inflation, commodity, and cross-asset composite products. These products range from cash and physical plain vanilla products to exotic and complex derivative products. Also included is a set of mathematical valuation models for these products, and their associated market data, payment and accounting entries generation routines and their associated observables, calibration models and their associated raw inputs. 
     By way of another example, a set of one or more application programs and the runtime may implement a word processor, a spreadsheet, a communication/e-mail software, a photo viewing software, a virus scan software, a media player, a database server, a game, an industrial application, and/or an operating system. Of course, application programs can be implemented to perform a variety of other tasks. 
     Exemplary Implementations 
     By way of illustration, exemplary embodiments of the invention will be described that support dependencies, dynamic dependencies (including contingent dependencies and subscription dependencies), explicit dependency determination producers for shortcut declared dependencies and for non-shortcut declared dependencies, on the fly dependency determination producers for shortcut declared dependencies, class keys, instance keys, method keys, producer override/unoverride commands (which are types of set commands), and global execute commands. In addition, the exemplary embodiments optionally support a producer graph interactive viewer module and incremental execution. Of course, alternative embodiments of the invention may implement more, less, and/or different features. 
       FIG. 10  is a block diagram of an exemplary implementation according to one embodiment of the invention. In  FIG. 10 , dashed dividing line  1000  separates a runtime client  1002  from a runtime with producer graph oriented programming support  1004 . 
     The logical execution flow of the runtime client  1002  includes blocks  1010 ,  1020 ,  1025 ,  1030 , and  1035 , and the runtime with producer graph oriented programming support  1004  includes respectively corresponding blocks  1095 ,  1098 ,  1040 ,  1045 ,  1070 , and  1082 ; while a solid arrowed line represents a direct causal relationship from block  1035  of the logical execution flow of the runtime client  1002  to block  1070  of the runtime with producer graph oriented programming support  1004 , dotted arrowed lines illustrate a causal relationship from blocks  1010 ,  1020 ,  1025 , and  1030  of the runtime client  1002  to blocks  1095 ,  1098 ,  1040 , and  1045  of the runtime with producer graph oriented programming support  1004 . Depending on the embodiment of the invention, these later causal relationships may be direct or indirect. For example, similar to  FIG. 6 , an optional indirect causation through the use of a command log (not shown) and/or override log  1047  may be used. Further blocks  1095  and  1098  are dashed because they may optionally be part of a different block depending on the embodiment of the invention (e.g., block  1095  may be part of block  1098 ; block  1090  may be part of block  1040 ; blocks  1095  and  1090  may be part of block  1040 ). Similarly, block  1045  is dashed because it may be optionally part of a different block depending on the embodiment of the invention (e.g., block  1045  may be part of block  1070 ). Likewise, block  1049  may be optionally part of a different block depending on the embodiment of the invention (e.g., block  1049  may be part of block  1040 ). In some embodiments, the runtime  1004  includes a metrics acquisition module  1082 . The metrics acquisition module  1082  may optionally be part of block  1070 . 
     In  FIG. 10 , the runtime  1002  includes class definitions that include business logic  1010  having data  1012 , methods  1014 , execution mode setting  1015 , producer dependency declarations  1016 , and optionally class keys  1090 . The class definitions  1010  are classes in an object-oriented programming language, and thus include definitions for data  1012  and methods  1014 . The execution mode setting  1015  may specify at code level an execution mode in which the method is to be executed if the execution mode setting is not overridden later. In addition, these class definitions  1010  include producer dependency declarations  1016  for the method  1014  as previously described. Further, in one embodiment of the invention, each class has a class key  1090  for tracking purposes. 
     The new class module  1095  of the runtime  1004  loads and introspects the class definitions  1010  (e.g., responsive to new class commands). This loading and introspecting may be done using any number of well known or future developed techniques, including those to selectively load classes for optimization purposes. The loading of the classes by the new class module  1095  is illustrated by classes  1054  of the runtime  1004 . As part of loading and introspecting the classes  1054 , the new class module  1095  also loads and introspects the producer dependency declarations  1016  as illustrated by methods and producer dependency declarations  1056  in the classes  1054 . The new class module  1095  also maintains a class tracking structure  1092  that is used for tracking the classes using the class keys. Thus, the class tracking structure  1092  maintains a correspondence between class keys and references into the classes  1054 . In addition, the new class module  1095  also maintains a method tracking structure  1058  that is used for tracking methods using the method keys. Thus, the method tracking structure  1058  maintains a correspondence between method keys and references to the methods, as well as information regarding the producer dependency declarations. Further, the new class module  1095  may input the execution mode setting  1015  to the producer-based configurable decision structure  1049 , which maintains the execution modes for producers. 
     The runtime client  1002  also includes instance instantiation commands with instance keys  1020 . The new instance module  1098  of the runtime  1004  instantiates the instances designated by the instance instantiation commands with instance keys  1020  (e.g., responsive to new instance commands). This instantiation of instances may be done using any number of well known or future developed techniques, including those to selectively instantiate instances for optimization purposes. As part of this instantiation of instances, the new instance module  1098  accesses the class tracking structure  1092  using a class key to access the appropriate class from the classes  1054 . The instantiation of instances by the new instance module  1098  is illustrated by instances  1052  of the runtime  1004 . The new instance module  1095  also maintains an instance tracking structure  1065  that is used for tracking the instances using the instance keys. Thus, the instance tracking structure  1065  maintains a correspondence between instance keys and references into the instances  1052 . As previously indicated, the new class module  1095  may be part of the new instance module  1098  in that the classes  1054  may be instantiated responsive to the instance instantiation commands  1020 , as opposed to separate new class commands. 
     The runtime client  1002  also includes producer instantiation commands with producer keys  1025 . The automated producer graph generation module  1040  of the runtime  1004  loads producers designated by the producer instantiation commands with producer keys  1025  (e.g., responsive to new producer commands designating the current set of producers of interest). In addition, the automated producer graph generation module  1040  also discovers, builds, and optionally resolves the producer graph(s) responsive to the current set of producers of interest as previously described. In one embodiment of the invention, a producer key is comprised of a class key, instance key, and method key. As part of this instantiating of producers, the automated producer graph generation module  1040 : 1) accesses the class tracking structure  1092  using the class key to access the appropriate class from the classes  1054 ; 2) accesses the instance tracking structure  1065  using the instance key to access the appropriate instance from the instances  1052 ; and 3) accesses the method tracking structure  1058  using the method key to access the appropriate producer dependency declaration statement. The instantiating of the producers designated by the producer instantiation commands with producer keys  1025  and instantiating of the any discovered producers and building the producer graph is illustrated by producer graph(s) structure  1060  of the runtime  1004 . Thus, in one embodiment of the invention, the producer keys identified by the producer instantiation commands with producer keys  1025  and those discovered through producer graph generation are stored in the producer graph(s) structure  1060 , along with addition information to represent the current producer graph(s). 
     As previously described, the block  1095  and  1098  may be part of block  1040 , and thus, the decision regarding which classes, instances, and producers to load/instantiate is driven by what producers are in the current producer graph(s). In such an embodiment of the invention, the loading/instantiation of class, instances, and producers is optimized and is producer centric. 
     The runtime client  1002  also includes data preparation commands, including producer output override/unoverride commands  1030 . The override/unoverride commands include the producer key of the producer to be overridden/unoverriden, as well as the override values when being overridden. The override producer output module  1045  of the runtime  1004  causes producers designated by the producer override/unoverride commands to be overridden/unoverriden. This causation may be indirect or direct. 
     In the case of indirect causation, the override producer output module  1045  populates the override log  1047  for consumption by the producer graph execution module  1070 . In the case of direct causation, the override producer output module  1045  accesses the producer output caching  1097  of the producer graph(s) structure  1060  and the instances  1052 . Specifically, as described with reference to the override producer output module  390 , in one embodiment, producers can be classified as property producers or method producers; thus, the override producer output module  1045  may include an override property producer output module for overridden property producers and an override method producer output module for overridden method producers (not shown); the overriding of a property method causes the overridden value to be stored in the producer output caching  1097  of the producer graph(s) structure  1060  and to be stored in the data of the appropriate instance of the instances  1052 , whereas the overriding of a method producer causes the overridden value to be stored in the producer output caching  1097 . 
     In one embodiment of the invention producers may not be overridden before a producer graph of which they will be part has been initially executed (thus, the producer will already be instantiated as a result of being designated as a producer of interest or as a result of being discovered by the automated producer graph generation module  1040 ). However, in the embodiment shown in  FIG. 10 , producers may be overridden before the initial execution by being instantiated and overridden with a producer override command. Such an overridden producer will typically eventually become part of a producer graph through the discovery process (e.g., when a dynamic dependency is resolved). In some embodiments of the invention, this data preparation may also include other types of set commands. The override producer output module  1045  is shown as a dashed box because it may not be present in alternative embodiments of the invention. 
     The producer graph(s) structure  1060  also optionally includes incremental execution marking  1080  for some embodiments of the invention that support incremental execution. As previously described with reference to the incremental execution marking  382  of  FIG. 3B , the incremental execution markings  1080  is used to assist with incremental execution of the producer graph(s) on execution beyond that of the initial execution. Different embodiments of the invention that use the incremental execution marking  382 , use them in different ways. For example, in one such embodiment of the invention that has a command log, the log is used to track which producers have been added and/or modified, and the incremental execution marking  382  are used to mark those producers that are affected (ancestors of the modified or added producers, and thus dependent on them). As another example, in one such embodiment of the invention that does not have a command log, the incremental execution marking  382  are used to mark those producers that are added or modified, as well as those that are ancestors of the modified or added producers (and thus dependent on them). As another example, in one such embodiment of the invention that does not have a command log, modifications and additions of producers are done immediately and the incremental execution marking  382  are used to mark those producers that are ancestors of the modified or added producers (and thus dependent on them). While embodiments of the invention have been described that support incremental execution and use incremental execution marking, other embodiments of the invention support incremental execution that do not use incremental execution marking (e.g., a command log is used to track which producers were added or modified, and a list of execution start producers is maintained in an execution start log; where the producer graph execution module  1070  starts from the execution start producers and works its way up the ancestors of the producer graph(s) to the top; by way of example and not limitation, this embodiment of the invention is described later herein with regard to  FIGS. 15-25 . 
     The runtime client  1002  also includes execution mode selection commands  1036  according to some embodiments of the invention. A user may use the execution mode selection commands  1036  to change the execution mode setting(s) by changing the runtime setting structure  1048 , the producer-based configuration decision structure  1049 , and/or the producer graph structure  1060 . In one embodiment, the execution mode selection commands  1036  change the producer-based configuration decision structure  1049  to modify the execution mode settings of a particular class, a particular instance, a particular method, or any combination of the above. For example, a first execution mode selection command may change the execution mode setting of all methods of a particular class to a first execution mode, a second execution mode selection command may change the execution mode setting of a particular instance of a particular class, a third execution mode selection command may change the execution mode setting of a particular method, a fourth execution mode selection command may change the execution mode setting of a particular method and a particular instance, and so on. Alternatively, a user may use the execution mode selection commands  1036  to change the execution mode setting(s) on a producer-by-producer basis by changing the producer graph structure  1060 . Since each producer in the producer graph structure  1060  has a producer execution mode setting, the execution mode selection commands  1036  may provide a producer key identifying a particular producer and a desired execution mode setting for the particular producer to cause the runtime  1004  to change the execution mode setting for the particular producer to the desired execution mode setting. 
     The runtime client  1002  also includes global execution commands  1035 . The producer graph execution module  1070  of the runtime  1004  executes the producer graph(s). The producer execution module  1070  may execute each producer in the producer graph(s) based on the corresponding execution mode of the producer from the producer-based configuration structure  1049 . In some embodiments, the producer execution module  1070  may override the execution mode of a predetermined producer from the producer-based configuration structure  1049 . For instance, if the execution mode from the producer-based configuration structure  1049  is not supported by the runtime  1004 , then the producer execution module  1070  may override such execution mode. 
     In some embodiments, the runtime  1004  supports three execution modes namely, multiprocessing, multithreading, and local execution. Thus, the producer execution module  1070  includes a parallelization module  1076 , a multiprocessing module  1077 , a multithreading module  1078 , and a local execution module  1079 . For each producer, the automatic producer graph generation module  1040  may find the corresponding execution mode from the producer-based configuration decision structure  1049  and may set the producer execution mode setting accordingly in the producer graph structure  1060  if the corresponding execution mode is not overridden by a runtime setting in the runtime setting structure  1048 . Based on the producer execution mode setting in the producer graph structure  1060 , the parallelization module  1076  may send the producer to a corresponding one of the multiprocessing module  1077 , the multithreading module  1078 , and the local execution module  1079 . Then a task may be instantiated for the producer at the multiprocessing module  1077 , the multithreading module  1078 , and/or the local execution module  1079 . A task is a logically high level, discrete, independent section of computational work. A task is typically executed by a processor as a program. 
     In some embodiments, if the execution mode is multiprocessing, then the parallelization module  1076  may send the producer to the multiprocessing module  1077 . The multiprocessing module  1077  may serialize the task corresponding to the producer as well as the inputs to the producer, and add the serialized task and inputs to a job. When the tasks corresponding to all ready to be executed producers having an execution mode of multiprocessing have been added to the job, the multiprocessing module  1077  may send the job to a grid dispatcher  1081  to be forwarded to a grid of processors. Then some or all of the processors in the grid may execute the tasks in the job distantly. If the execution mode is multithreading, then the parallelization module  1076  may send the producer to the multithreading module  1078 . The multithreading module  1078  may initiate a thread pooling mechanism and feed the task corresponding to the producer to an available thread to be executed. If the execution mode is local execution, then the parallelization module  1076  may send the producer to the local module  1079 . The local module  1079  may then execute the task within the current runtime thread. 
     In some embodiments, the parallelization module  1076  may send a producer to a predetermined one of the multiprocessing module  1077 , the multithreading module  1078 , and the local execution module  1079  by default if no execution mode has been specified for the producer. On the other hand, if the class definition  1010  of the producer includes an execution mode setting  1015  for the producer, the parallelization module  1076  may send the producer according to the execution mode setting  1015  unless the execution mode setting  1015  is overridden. The execution mode setting  1015  may be overridden in various ways. In one embodiment, the execution mode selection commands  1036  changes the execution mode settings in the producer-based configurable decision structure  1049  on a class basis, a method basis, an instance basis, or any combination of the above, to override the execution mode setting  1015 . In one embodiment, the execution mode selection commands  1036  changes the execution mode settings on a producer-by-producer basis in the producer graph structure  1060  to override the execution mode setting determined using the producer-based configurable decision structure  1049 . In one embodiment, the execution mode selection commands  1036  changes the execution mode settings on a runtime global level in the runtime setting structure  1048  to override the execution mode settings in the producer graph structure  1060 . 
     As such, the producer graph execution module  1070  modifies the producer output caching  1097  (in the case of property producers and method producers), uses the incremental execution marking  1080  (if present), and modifies the data of the instances  1052  (in the case of property methods). In some embodiments, the metrics acquisition module  1082  may acquire metrics during execution of the producers. The metrics acquired may be stored in metrics  1083  in the producer graph(s) structure  1060 . Note that the metrics may be acquired on a producer basis, and since a producer includes a unique combination of a class, a method, and an instance, the metrics acquired may be on a class-instance-method basis. Furthermore, the metrics acquired may be on a task basis and/or on a job basis. 
     In some embodiments, the metrics acquired include different types of metrics for different usages, such as for monitoring the computing environment, for monitoring distant execution time, for monitoring local execution time, for monitoring data streams, for monitoring overall execution time, for benchmarking different types of execution, etc. For example, to monitor the computing environment, metrics such as the number of processors or engines available on a remote grid used in multiprocessing and dedicated to execution of the producers and an empirical ratio observed between local and distant processing times may be acquired. For instance, if the local processor and the distant processor are not overloaded with other tasks, this empirical ratio may be close to the frequency ratio between the two processors. To monitor distant execution time, metrics such as distant processing time, distant deserialization time, and distant serialization time may be acquired. To monitor local execution time, metrics such as local execution time, local deserialization time, and local serialization time may be acquired. To monitor data streams, metrics such as size of serialized input objects and size of serialized output objects may be acquired. When processing data on distant processors, input and output data are exchanged over a network. The efficiency of the distant processing is directly linked to the data volume being exchanged. Monitoring the size of data streams may provide useful information to help reduce or avoid overloading the data structures being exchanged with redundant or useless information. To monitor overall execution time, metrics such as the overall time to execute a specific producer may be acquired. In some embodiments, the overall time to execute a specific producer may be the sum of local serialization time, distant deserialization time, distant processing time, distant serialization time, and local deserialization time. This time may be measured on a task-by-task basis, and may be fairly consistent (i.e., the times are very close) across all the tasks pertaining to a single job. To benchmark different types of execution, comparison metrics such as speedup and efficiency may be derived from other metrics acquired. Speedup is a measure of how much a parallel algorithm is faster than a corresponding sequential algorithm. Speedup is defined for a particular job as the sum of local processing times of all tasks (if executed locally) pertaining to the job divided by the job execution time (Job Overall time) using a parallel execution approach, such as multiprocessing. Theoretically, an ideal speedup is reached when speedup substantially equals to the number of processors, that is, when serialization times and deserialization times are close to zero, or compensated by a favorable processor efficiency ratio. The efficiency equals to 100*speedup/number of processors. Again, in a theoretically ideal situation where local and distant processors are identical, the ideal efficiency is close to 100%. 
     Various techniques have been previously discussed for executing the producers of the producer graph and are applicable here. For instance, in embodiments in which a command log is implemented, the command log is consumed and then the producer graph(s) are executed. Further, in embodiments of the invention that support the possibility of unresolved dependencies, producer graph execution module  1070  includes dynamic dependency module  1075 , which can invoke the automated producer graph generation module  1040 . 
       FIG. 10  also shows an optional producer graph viewer module  1062  that provides a mechanism (e.g., a GUI) by which a programmer/user can view the producer graph(s) and producer outputs of the producer graph(s) structure. Further,  FIG. 10  shows an optional configurable interactive producer output layout graphical user interface module  1085  to provider for a graphical user interface (GUI) (including dynamic invocation of blocks  1030 , and  1035 ) that represents the configurable interactive producer output layout graphical user interface module  840 . 
     In embodiments of the invention that use a command log, different triggers may be use to trigger different actions. For instance, the producer instantiation commands may be logged and batch processed responsive to an explicit command (start logging and end logging), an explicit global execute command (logging starts automatically at startup and after each explicit global execute command, and each log is processed responsive to the following explicit global execute command), an explicit data preparation command, etc. Similarly, the data preparation commands may be logged and batch processed responsive to an explicit global execute command, a first get command, every get command, etc. 
     Exemplary Tracking Structures 
       FIGS. 11A-G  are block diagrams illustrating exemplary content of the data structures of  FIG. 10  according to one embodiment of the invention. While  FIGS. 11A-G  illustrate these data structures as tables, it should be understood that any suitable data structure may be used (e.g., a hash map, a set, a list, etc.). 
       FIG. 11A  is a block diagram of an example of the class tracking structure  1092  of  FIG. 10  according to one embodiment of the invention. In  FIG. 11A , a class key column  1110  and a class reference column  1115  are shown to respectively store the class keys and corresponding references to the loaded classes. 
       FIG. 11B  is a block diagram of an example of the instance tracking structure  1065  of  FIG. 10  according to one embodiment of the invention. In  FIG. 11B , an instance key column  1120  and an instance reference column  1125  are shown to respectively store the instance keys and corresponding references to the instances. In embodiments of the invention in which instance keys need not be unique across all classes, the instance tracking structure also include the class key or reference for the class of the instance 
       FIG. 11C  is a block diagram of an example of the producer graph(s) structure  1060  of  FIG. 10  according to one embodiment of the invention. In  FIG. 11C , a class reference column  1135 , an instance reference column  1140 , and a method reference column  1145  are shown to respectively store references that make up the current producers of the current producer graph(s). These references may take a variety of forms. For example, these columns may respectively store references into the classes  1054  (or alternatively  1092 ), instances  1052  (or alternatively  1065 ), and methods  1056  (or alternatively  1058 ). While in one embodiment of the invention these columns store references, in alternative embodiment of the invention one or more of these columns store keys. 
     In addition,  FIG. 11C  includes a parent producer(s) link(s) column  1150  (including for each link a parent producer reference, and a dependency determination producer reference) and a child producer(s) link(s) column  1160  (including for each link, child producer reference(s), a dependency determination producer reference, a link mode, and a sticky link indicator). Each producer may have zero or more child producer links in column  1160 . Each child producer link in column  1160  includes: 1) child producer reference(s) which are references to other rows of the producer graph(s) structure to represent a producer dependency according to the producer dependency declaration; 2) a dependency determination producer reference which is a reference to another row of the producer graph(s) structure and represents the dependency determination producer that has created the child link; and 3) a link mode with a producer dependency type that identifies whether the producer dependency is a result of an argument, a field, or a sequencing dependency (see discussion regarding  FIGS. 7A-F ), and if an argument, the argument ID of the producer dependency; and 4) a sticky indicator to indicate that the link mode is the result of an upwardly declared dependency (in embodiments of the invention that support upwardly declared dependencies) or the result of a sticky subscription (in embodiments of the invention that support sticky subscriptions) and should not be modified through the producer argument dependency declaration of this producer (i.e., the producer stored in the row of the column containing the sticky indicator). Each producer may have zero or more parent producer links in column  1150 . Each parent producer link in column  1150  includes: 1) a parent producer reference that stores back a reference in accordance with a child producer reference of another producer (i.e., a reference to another row of the producer graph(s) structure to represent a parent producer dependent on this producer); and 2) a dependency determination producer reference which is a reference to another row of the producer graph(s) structure and represents the dependency determination producer which has created the parent link. Thus, when a link is created, the parent producer link column of the child producer&#39;s row and the child producer link column of the parent producer&#39;s row are modified to represent the link (and the dependency determination producer reference is the same in both). In one embodiment of the invention, since multiple paths in a producer graph or different producer graphs may include a given producer, there may be multiple parent producer links for a given producer. 
     Further,  FIG. 11C  includes a producer output caching and override producer output modification column  1170  to store the current producer outputs, as well as an indication of whether the producer is overridden and the overridden output value. Also,  FIG. 11C  includes an incremental execution marking column  1180  to store incremental execution markings as previously described. 
     In some embodiments,  FIG. 11C  includes a producer execution mode setting column  1173  to store the execution mode setting of each producer in the producer graph structure  1060 . For example, the execution mode setting may be one of multiprocessing, multithreading, and local execution. 
     Further,  FIG. 11C  includes a producer metrics column  1175  to store metrics of each producer in the producer graph structure  1060 . The producer metrics are acquired on a producer-by-producer basis using the metrics acquisition module  1082 . Details of some embodiments of the process to acquire metrics are discussed below. 
       FIG. 11D  is a block diagram of an example of the method tracking structure  1058  of  FIG. 10  according to one embodiment of the invention. In  FIG. 11D , a method key column  1190  and a method reference column  1192  are shown to respectively store the method keys and corresponding references to the methods of the loaded classes. In addition,  FIG. 11D  also includes an ArgumentDependencies column  1194 , a FieldDependencies column  1196 , a SequencingDependencies column  1195 , an UpwardDependencies column  1193 , a WeaklyConstrainedDependencies column  1199 , an output class column  1197 , and an optional additional annotations column  1198  including a default execution mode. The ArgumentDependencies column  1194 , the SequencingDependencies column  1195 , the UpwardDependencies column  1193 , the WeaklyConstrainedDependencies column  1199 , and the FieldDependencies column  1196  store producer dependency information parsed from the producer dependency declaration statement of the method (e.g., see  705  of  FIG. 7A ), while the output class column  1197  stores information regarding the output class of the output of the method (determinable by the method&#39;s signature—e.g., see  710  of  FIG. 7A ). Exemplary contents of the ArgumentDependencies column  1194 , FieldDependencies column  1196 , SequencingDependencies column  1195 , UpwardDependency column  1193 , and WeaklyConstrainedDependencies column  1199 , used in some embodiments of the invention are provided later herein. 
       FIG. 11E  is a block diagram of an example of a serialized form local map according to one embodiment of the invention. The serialized form local map in  FIG. 11E  includes a serialized form identifier (ID) column  1112 , an input producer key column  1113 , an underlying class key and instance key column  1114 , a serialized form  1116 , a serialized form size  1117 , and a serialization time  1118 . In some embodiments, the serialized form ID, the input producer key, the underlying instance key, and the serialized form are used to implement parallelization by the runtime  1004 . Details of the implementation are discussed below. In some embodiments, the runtime  1004  implements instrumentation to acquire metrics on a producer basis. Thus, the runtime  1004  may store the serialized form size and the serialization time in the columns indicated by dashed lines in the serialized form local map. Details of instrumentation are discussed below. 
       FIG. 11F  is a block diagram of an example of the runtime setting structure  1048  of  FIG. 10  according to one embodiment of the invention. The table includes an original execution mode column  1121  and a final execution mode column  1123 . If an execution mode is not overridden on the runtime global level, the final execution mode is the same as the original execution mode. On the other hand, if the execution mode is overridden on the runtime global level, the final execution mode is different from the original execution mode. For instance, if the runtime  1004  does not support multiprocessing, then multiprocessing may be overridden on the runtime global level by assigning local execution to be the final execution mode of multiprocessing. 
       FIG. 11G  is a block diagram of an example of the producer-based configuration decision structure  1049  in  FIG. 10 . The table includes a class key column  1182 , a method key column  1184 , an instance key column  1186 , an execution mode setting column  1188 . The execution mode selection commands  1036  may modify the execution mode setting in the producer-based configuration decision structure on the basis of a class, a method, an instance, or any combination of the above. Thus, one or more of the class key column  1182 , method key column  1184 , and instance key column  1186  may be empty in a particular row according to one embodiment of the invention. 
     Distant Computing 
     As previously described, one embodiment of the invention supports an execution mode of multiprocessing. To support multiprocessing, the runtime may interact with a grid of processors by serializing tasks of producers, as well as inputs and/or an underlying instance of each producers, and sending the serialized form to the grid to be processed by the processors in the grid. 
       FIG. 12A  is a block diagram illustrating additional detail of  FIG. 10  to support multiprocessing according to one embodiment of the invention. To the left of the dashed dividing line  1200  is the runtime with producer graph oriented programming support  1004 . To the right of the dashed dividing line  1200  is a grid  1290 . On the side of the runtime  1004 ,  FIG. 12A  includes from  FIG. 10  the producer graph execution module  1070  (including the parallelization module  1076 , the multiprocessing module  1077 , the multithreading module  1078 , and the local execution module  1079 ) and the grid dispatcher  1081 . On the side of the grid  1290 ,  FIG. 12A  includes a distant computing module  1270 . 
     According to one embodiment of the invention, if an execution mode of a producer is multiprocessing, the parallelization module  1076  sends the producer to the multiprocessing module  1077 . The multiprocessing module  1077  may instantiate a job, which may include multiple tasks. The multiprocessing module  1077  may instantiate a task for the producer. The multiprocessing module  1077  may further serialize the task, as well as the inputs to the producer and/or an underlying instance of the producer. Then the multiprocessing module  1077  may add the serialized form of the task to the job. The multiprocessing module  1077  may send the job to the grid dispatcher  1081 . Then the grid dispatcher  1081  may send the job to the distant computing module  1270  of the grid  1290 . Details of the processing of the job by the grid  1290  are discussed below. 
     After the job has been processed, serialized outputs and/or instances of the tasks within the job are returned to the grid dispatcher  1081 . The grid dispatcher  1081  may forward the serialized outputs and/or instances of the tasks within the job to the multiprocessing module  1077  to be deserialized. 
     Dynamic Producer Dependencies 
     As previously described, one embodiment of the invention supports non-dynamic and dynamic producer dependencies. While different embodiments may support different types of dynamic producer dependencies, one embodiment of the invention supports contingent and subscription types of dynamic producer dependencies. Thus, a non-contingent, non-subscription dependency is a non-dynamic (static) dependency. 
       FIG. 12B  is a block diagram illustrating additional detail of  FIG. 10  to support contingent and subscription type dynamic producer dependencies according to one embodiment of the invention.  FIG. 12B  includes from  FIG. 10  the dashed dividing line  1000 , the class definitions that include business logic  1010  (which include data  1012 , methods  1014 , and producer dependency declarations  1016 ), the new class module  1095 , the classes  1054  (including methods and producer dependency declarations  1056 ), the new instance module  1098 , the instances  1052 , the instance tracking structure  1065 , the automated producer graph generation module  1040 , the producer graph(s) structure  1060 , and the producer graph execution module  1070  (including the dynamic dependency module  1075 ). 
       FIG. 12B  shows that the producer dependency declarations  1016  optionally include contingent dependencies  1210 , subscription dependencies  1220 , and multiple producers  1215 . Here, multiple producers  1215  refers to the ability of a producer dependency to return a collection of producers. In addition,  FIG. 12B  includes a subscription module  1240  and a contingency module  1230  in the automated producer graph generation module  1040  to process the contingent dependencies  1210  and subscription dependencies  1220 .  FIG. 12B  also shows that the subscription module  1240  accesses a subscription log  1250 . Further, the dynamic dependency module  1075  includes a contingency module  1260  and a subscription module  1265  to process the contingent dependencies  1210  and subscription dependencies  1220 . The subscription module  1265  accesses the subscription log  1250 . 
     The following description of contingent and subscription dependencies is done in the context of an embodiment of the invention that uses a class DEP (an abbreviation for dependency), from which an instance is returned by dependency determination producers and is analyzed by the runtime with producer graph oriented programming support. The class DEP includes the following fields: 1) TYPE which can be set to subscription, non-subscription downwardly declared (child producers that are not subscriptions), or non-subscription upwardly declared (parent producers that are not subscriptions); 2) PROD which is used for non-subscription downwardly declared dependencies and is a collection of child producers (as such, it can store zero or more producers); 3) SUB TYPE which is used for subscription dependencies and is set to indicate the type of subscription dependency (used in embodiments of the invention that support multiple types of subscription; while the embodiment of the invention described here can support two types—sticky and absorbing, alternative embodiments may support more, less, and/or different subscription types; 4) SUB CRIT which is used for subscription dependencies and is set to indicate the subscription criteria; 5) PAR LINK MODE which is used for sticky subscription dependencies and non-subscription upwardly declared dependencies and is set to indicate what the link mode of the parent producer should be; 6) PAR CLASS which is used for sticky subscription dependencies and non-subscription upwardly declared dependencies and is set to indicate what the class of the parent producer (e.g., the class key) should be; 7) PAR METHOD which is used for sticky subscription dependencies and non-subscription upwardly declared dependencies and is set to indicate what the method of the parent producer (e.g., the method key) should be; and 8) PAR INSTANCE which is used for sticky subscription dependencies and non-subscription upwardly declared dependencies and is set to indicate what the instance of the parent producer (e.g., the instance key) should be (If PAR INSTANCE is left blank, the instance key of the child producer is then used for the parent producer). An alternative embodiment could use a collection of parent producers (each item of the collection holding a PAR_CLASS, PAR_INSTANCE, PAR_METHOD, PAR_LINK MODE) in the case of sticky subscription dependencies and/or non-subscription upwardly declared dependencies. Of course, other alternative embodiments of the invention could use a different structure to return dependencies. 
     Contingent Dependencies 
     In one embodiment of the invention, both non-contingent and contingent producer dependencies are supported. A non-contingent producer dependency is one that is independent of the output of other producers, while a contingent producer dependency is one that is dependent on the output of other producers. While one embodiment of the invention supports both non-contingent and contingent producer dependencies, alternative embodiments support only non-contingent or contingent (which contingent producer dependencies may be initially driven by default values). 
     As previously discussed, a producer can be viewed as a set of multiple identifiers, one identifier for each additional level of granularity specified. In one embodiment of the invention, a contingent producer dependency can be contingent in the sense that any one or all of the set of identifiers can be conditionally determined based on current data values. For instance, a first contingent producer dependency may have only the instance identifier be conditionally determined (the class and method identifiers are fixed), while a second contingent producer dependency may have the class, instance, and method identifiers be conditionally determined. While in one embodiment of the invention, all of the plurality of identifiers of a contingent producer dependency may be conditional, alternative embodiments of the invention may be implemented differently (e.g., only allow a subset of the plurality of identifiers to be conditional). 
       FIGS. 13A-J  are block diagrams illustrating pseudo code and exemplary producers according to one embodiment of the invention. In addition, the embodiments shown in  FIG. 13A-J  use the same dependency determination mechanism for both contingent and non-contingent dependencies. As such, for explanation purposes, some of the examples in  FIGS. 13A-J  are examples of non-contingent dependencies, while the others are examples of contingent producer dependencies. Further, a non-contingent producer dependency is one in which the dependency is to a dependency determination producer that is an independent producer (e.g., in one embodiment of the invention, the dependency type is identifiable because its producer dependency declaration is empty); while a contingent producer dependency is one in which the dependency is to a dependency determination producer that is a dependent producer (e.g., in one embodiment of the invention, the dependency type is identifiable because its producer dependency declaration is non-empty). 
     Further, circled numbers and letters are used in  FIGS. 13A-J  to illustrate the order in which operations are performed according to one embodiment of the invention. Also, a notation X::Y::Z is used in  FIGS. 13A-J  to represent a producer key made up of a class key (X), an instance key (Y), and a method key (Z). Further dashed circles and arrowed lines represent operations that are not performed in some embodiments of the invention. In particular, where the execution of an independent dependency determination producer for a given dependency will always return the same dependency (e.g., an independent dependency determination producer), such dependency determination producer in some embodiments of the invention is executed but not instantiated and linked in the producer graph(s). 
     Explicit Dependency Determination Producers 
       FIG. 13A  illustrates pseudo code of producer dependency declarations for methods using a non-shortcut declared, non-dynamic (non-contingent, non-subscription) dependency according to one embodiment of the invention; while  FIG. 13B  is a block diagram of producers illustrating an exemplary non-shortcut declared, non-dynamic (non-contingent, non-subscription) producer dependency according to one embodiment of the invention.  FIG. 13A  shows: 1) a producer dependency declaration statement  1300  for a method alpha  1305 , where the producer dependency declaration statement  1300  includes a producer dependency to a producer CW::IY::BETA; and 2) a producer dependency declaration statement  1310  for a method beta  1315 , where the producer dependency declaration statement  1310  is empty, and where the method beta  1315  returns as an argument an instance of the class DEP. The method beta  1315  includes producer dependency declaration code  1320  that sets DEP.TYPE to non-subscription downwardly declared, sets DEP.PROD to producer  13 , and returns DEP. 
     In  FIG. 13A , a circled  1  indicates that the producer dependency declaration  1300  is accessed (e.g., as a result of designation of a producer based on the method alpha  1305  as a producer of interest, as a result of automated discovery of a producer based on the method alpha  1305 , as a progeny of a producer of interest, etc.). A circled  2  in  FIG. 13B  shows that a producer C 0 ::I 0 ::ALAPHA is instantiated based on the method alpha  1305 . A circled  3  in  FIG. 13A  indicates that the producer dependency to producer CW::IY::BETA is processed to determine the producer dependency, and as a result, a circled  4  indicates that the producer dependency declaration  1310  is accessed. A dashed circled  5  in  FIG. 13B  shows that a producer CW::IY::BETA is instantiated as a dependency determination producer  1380 . A dashed circled  6  in  FIG. 13B  indicates that the producer C 0 ::I 0 ::ALPHA is linked in the producer graph to indicate that producer CW::IY::BETA is a child producer. A circled  7  in  FIG. 13B  indicates that the producer CW::IY::BETA is executed and returns DEP to identify producer  13 . A circled  8  indicates producer  13  is instantiated, while a circled  9  indicates the producer  13  being linked as a child producer in the producer graph to the producer C 0 ::I 0 ::ALPHA. In  FIG. 13B , producer C 0 ::I 0 ::ALPHA and producer  13  are standard producers  1385  (they are not dependency determination producers). 
       FIG. 13C  illustrates pseudo code of producer dependency declarations for methods using a non-shortcut declared, contingent, non-subscription producer dependency according to one embodiment of the invention; while  FIG. 13D  is a block diagram of producers illustrating an exemplary non-shortcut declared, contingent, non-subscription producer dependency according to one embodiment of the invention. In addition,  FIG. 13D  refers to the producers  5 ,  7 A, and  7 B of  FIG. 5A  and the resolution of the dynamic dependency of producer  5  to the producer  7 A. 
       FIG. 13C  shows: 1) a producer dependency declaration statement  1300  for a method alpha  1305 , where the producer dependency declaration statement  1300  includes a producer dependency to a producer CW::IY::BETA; 2) a producer dependency declaration statement  1325  for a method beta  1315 , where the producer dependency declaration statement  1325  includes a producer dependency to a producer CU::IV::DELTA, and where the method beta  1315  returns as an argument an instance of the class DEP; 3) a producer dependency declaration statement  1332  for a method delta  1334 , where the producer dependency declaration statement  1332  is empty, and where the method delta  1334  returns as an argument an instance of the class DEP; and 4) a producer dependency declaration statement  1338  for a method gamma  1340 , where the producer dependency declaration statement  1338  is empty, and where the method gamma  1340  returns a variable X (where X is from an external source, a default value (explicit or constant in the class). The method beta  1315  includes producer dependency declaration code  1330  that sets DEP.TYPE to non-subscription downwardly declared, sets DEP.PROD to producer  7 A or  7 B depending on the output of producer CX::IZ::GAMMA, and returns DEP. The method delta  1332  includes producer dependency declaration code  1336  that sets DEP.TYPE to non-subscription downwardly declared, sets DEP.PROD to the producer CX::IZ::GAMMA, and returns DEP.PROD. 
     In  FIG. 13C , a circled  1  indicates that the producer dependency declaration  1300  is accessed (e.g., as a result of designation of a producer based on the method alpha  1305  as a producer of interest, as a result of automated discovery of a producer based on the method alpha  1305  as a progeny of a producer of interest, etc.). A circled  2  in  FIG. 13D  shows that the producer  5  is instantiated based on the method alpha  1305 . A circled  3  in  FIG. 13C  indicates that the producer dependency to producer CW::IY::BETA is processed to determine the producer dependency, and as a result, a circled  4  indicates that the producer dependency declaration  1325  is accessed. A circled  5  in  FIG. 13D  shows that a producer CW::IY::BETA is instantiated as a dependency determination producer  1380 . A circled  6  in  FIG. 13D  indicates that the producer  5  is linked in the producer graph to indicate that producer CW::IY::BETA is a child producer. 
     A circled  7  in  FIG. 13C  indicates that the producer dependency to producer CU::IV::DELTA is processed to determine the producer dependency, and as a result, a circled  8  indicates that the producer dependency declaration  1332  is accessed. A dashed circled  9  in  FIG. 13D  shows that a producer CU::IV::DELTA is instantiated as a dependency determination producer  1380 . A dashed circled  10  in  FIG. 13D  indicates that the producer CW::IY::BETA is linked in the producer graph to indicate that producer CU::IV::DELTA is a child producer. A circled  11  in  FIG. 13D  indicates that the producer CU::IV::DELTA is executed and returns DEP to identify CX::IZ::GAMMA. A circled  12  indicates that the producer CX::IZ::GAMMA is instantiated, while a circled  13  indicates the producer CX::IZ::GAMMA being linked as a child producer in the producer graph to the producer CW::IY::BETA. 
     In  FIG. 13D , a circled A indicates that the producer CX::IZ::GAMMA is executed and returns X to producer CW::IY::BETA, while a circled B indicates that the producer CW::IY::BETA returns DEP to identify producer  7 A; a circled C indicates that the unresolved remainder (method beta)  1390  is now resolved and producer  7 A is instantiated, while a circled D indicates the linking of the producer  5  to the producer  7 A. In  FIG. 13D , producers CX::IZ::GAMMA,  5 , and  7 A are standard producers  1385 . 
     On the Fly Dependency Determination Producers 
       FIG. 13E  illustrates pseudo code of producer dependency declarations for methods using both a non-shortcut declared, contingent, non-subscription producer dependency and a shortcut declared, contingent, non-subscription producer dependency according to one embodiment of the invention; while  FIG. 13F  is a block diagram of producers illustrating a non-shortcut declared, contingent, non-subscription producer dependency and a shortcut declared, contingent, non-subscription producer dependency according to one embodiment of the invention. Similar to  FIGS. 13D ,  FIG. 13F  refers to the producers  5 ,  7 A, and  7 B of  FIG. 5A  and the resolution of the dynamic dependency of producer  5  to the producer  7 A. 
       FIGS. 13E-F  are the same as  FIGS. 13C-D , with the exceptions: 1) a producer dependency declaration statement  1342  replaces the producer dependency declaration statement  1325 ; 2) a method fly  1344  replaces the method delta  1334 ; and 3) a producer CW::IY::FLY replaces the producer CU::IV::DELTA. The producer dependency declaration statement  1342  includes a shortcut declared producer dependency to the CX::IZ::GAMMA. Thus, the circled  4  in  FIG. 13E  now indicates that the producer dependency declaration  1342  is accessed. The circled  7  in  FIG. 13E  now indicates that the shortcut declared producer dependency to producer CX::IZ::GAMMA is processed to determine the producer dependency, and as a result, the runtime invokes the dependency determination producer CW::IY::FLY on the fly based on the method fly  1344 . The circled  8  now indicates that the producer dependency declaration  1332  is accessed. The dashed circled  9  in  FIG. 13F  now shows that the producer CW::IY::FLY is instantiated. The dashed circled  10  in  FIG. 13F  indicates that the producer CW::IY::BETA is linked in the producer graph to indicate that producer CW::IY::FLY is a child producer. The circled  11  in  FIG. 13F  indicates that the producer CW::IY::FLY is executed and returns DEP to identify CX::IZ::GAMMA. The remainder of  FIGS. 13E-F  is the same as  FIGS. 13C-D . 
     The on the fly generation by the runtime of the dependency determination producer CW::IY::FLY alleviates the application programmer from having to write explicit producer dependency declaration code and instantiate a dependency determination producer based thereon. Further, it allows the application programmer to directly specify the dependency on producer CX::IZ::GAMMA in the producer dependency declaration statement for the method beta  1315 , as opposed to specifying the dependency determination producer CU::IV::DELTA. 
     The shortcut technique can be used in a variety of situations, and may additionally have a variety of formats. For example, while in  FIGS. 13E-F  the shortcut declared dependency is for a non-contingent dependency (it directly identifies the child producer) and is in a producer dependency declaration statement for a method on which a dependency determination producer is based, other situations and formats are shown as follows: 1)  FIGS. 13G-H  illustrate the use of two shortcuts, where one is contingent and is part of a producer dependency declaration statement for a method on which a standard producer is based and the other is non-contingent and is part of a producer dependency declaration statement for a method on which a dependency determination producer is based; and 2)  FIGS. 13I-J  illustrate the use of a shortcut that is non-contingent and that is in a producer dependency declaration statement for a method on which a parent standard producer is based. 
       FIG. 13G  illustrates pseudo code of producer dependency declarations for methods using a shortcut declared, contingent, non-subscription producer dependency and a shortcut declared, non-contingent, non-subscription producer dependency according to one embodiment of the invention; while  FIG. 13H  is a block diagram of producers illustrating an exemplary shortcut declared, contingent, non-subscription producer dependency and a shortcut declared, non-contingent, non-subscription producer dependency according to one embodiment of the invention.  FIG. 13G  shows: 1) a producer dependency declaration statement  1345  for the method alpha  1305 , where the producer dependency declaration statement  1345  includes a shortcut declared, contingent producer dependency to a producer &lt;P&gt;GETC 1 ::I 1 ::M 1 ; 2) a producer dependency declaration statement  1350  for a method fly 1   1355 , where the producer dependency declaration statement  1350  includes a shortcut declared, non-contingent producer dependency to a producer C 0 ::I 0 ::GETC 1 , and where the method fly 1   1355  returns as an argument an instance of DEP; 3) the producer dependency declaration statement  1332  for a method fly 2   1362 , where the method fly 2   1362  returns as an argument an instance of DEP; and 4) the producer dependency declaration statement  1365  for a method getc 1   1370 , where the method getc 1   1370  returns C 1  with a value of CX or CY. 
     The method FLY 1   1355  and its producer dependency declaration statement  1350  are provided by the runtime responsive to the shortcut declared dependency &lt;P&gt;GETC 1 ::I 1 ::M 1  (which indicates that the shortcut is being used for the class key). The method fly 1   1355  includes producer dependency declaration code  1360  that sets DEP.TYPE to non-subscription downwardly declared, sets DEP.PROD to producer CX::I 1 ::M 1  or CY::I 1 ::M 1  depending on the value of C 1  output by the producer C 0 ::I 0 ::GETC 1 , and returns DEP. While in the example of  FIG. 13H , a &lt;P&gt; is used to designate that it is the class key of the producer that is contingent, alternative embodiments of the invention could use other syntaxes. Further, while in the example of  FIG. 13H , a &lt;P&gt; is used to designate that it is the class key of the producer that is contingent, one embodiment of the invention supports having more and/or different ones of the identifiers that make up the producer key be indicated as contingent in this manner. 
     In  FIG. 13G , a circled  1  indicates that the producer dependency declaration  1345  is accessed (e.g., as a result of designation of a producer based on the method alpha  1305  as a producer of interest, as a result of automated discovery of a producer based on the method alpha  1305  as a progeny of a producer of interest, etc.). A circled  2  in  FIG. 13H  shows that the producer C 0 ::I 0 ::ALPHA is instantiated based on the method alpha  1305 . A circled  3  in  FIG. 13G  indicates that the shortcut declared producer dependency is processed to determine the producer dependency and the runtime provides the method fly 1   1355 ; and as a result, a circled  4  indicates that the producer dependency declaration  1350  is accessed. 
     A circled  5  in  FIG. 13H  shows that a producer C 0 ::I 0 ::FLY 1  is instantiated as a dependency determination producer  1380 . A circled  6  in  FIG. 13H  indicates that the producer C 0 ::I 0 ::ALPHA is linked in the producer graph to indicate that producer C 0 ::I 0 ::FLY 1  is a child producer. A circled  7  in  FIG. 13G  indicates that the shortcut declared producer dependency to producer C 0 ::I 0 ::GETC 1  is processed to determine the producer dependency and the runtime provides the method fly 2   1362 , and as a result, a circled  8  indicates that the producer dependency declaration  1332  is accessed. A dashed circled  9  in  FIG. 13H  shows that a producer C 0 ::I 0 ::FLY 2  is instantiated. A dashed circled  10  in  FIG. 13H  indicates that the producer C 0 ::I 0 ::FLY 1  is linked in the producer graph to indicate that producer C 0 ::I 0 ::FLY 2  is a child producer. 
     A circled  11  in  FIG. 13H  indicates that the producer C 0 ::I 0 ::FLY 2  is executed and returns DEP to identify producer C 0 ::I 0 ::GETC 1 . A circled  12  indicates that the producer C 0 ::I 0 ::GETC 1  is instantiated, while a circled  13  indicates that the producer C 0 ::I 0 ::GETC 1  being linked in the producer graph to the producer C 0 ::I 0 ::FLY 1  as a child producer. 
     In  FIG. 13H , a circled A indicates that the producer C 0 ::I 0 ::GETC 1  is executed and returns C 1 =CX to producer C 0 ::I 0 ::FLY 1 , while a circled B indicates that the producer C 0 ::I 0 ::FLY 1  is executed and returns DEP to identify producer CX::I 1 ::M 1 ; a circled C indicates that the unresolved remainder (method fly 1 )  1390  is now resolved, and a circled D indicates the linking of the producer C 0 ::I 0 ::ALPHA to the producer CX::I 1 ::M 1 . In  FIG. 13H , producers C 0 ::I 0 ::GETC 1 , C 0 ::I 0 ::ALPHA, and CX::I 1 ::M 1  are standard producers  1385 . 
     The on the fly generation by the runtime of the dependency determination producer C 0 ::I 0 ::FLY 1  and C 0 ::I 0 ::FLY 2  alleviates the application programmer from having to write explicit producer dependency declaration code and instantiate dependency determination producers based thereon. Further, it allows the application programmer to directly specify the contingent dependency on a producer **::I 1 ::M 1  through the method getC 1  in the producer dependency declaration statement for the method alpha  1305 , as opposed to specifying the dependency determination producer CW::IY::BETA. 
       FIG. 13I  illustrates pseudo code of producer dependency declarations for methods using a shortcut declared, non-dynamic (non-contingent, non-subscription) producer dependency according to one embodiment of the invention; while  FIG. 13J  is a block diagram of producers illustrating an exemplary shortcut declared, non-dynamic producer dependency according to one embodiment of the invention.  FIG. 13I  shows: 1) a producer dependency declaration statement  1372  for a method alpha  1305 , where the producer dependency declaration statement  1372  includes a shortcut declared producer dependency to a producer  10 ; and 2) a producer dependency declaration statement  1374  for a method fly  1376 , where the producer dependency declaration statement  1374  is empty, and where the method fly  1376  returns as an argument an instance of DEP. The method fly  1776  and its producer dependency declaration statement  1374  are provided by the runtime responsive to the shortcut declared dependency. The method fly  1376  includes producer dependency declaration code  1378  that sets DEP.TYPE to non-subscription downwardly declared, sets DEP.PROD to producer  10 , and returns DEP. 
     In  FIG. 13I , a circled  1  indicates that the producer dependency declaration  1372  is accessed (e.g., as a result of designation of a producer based on the method alpha  1305  as a producer of interest, as a result of automated discovery of a producer based on the method alpha  1305  as a progeny of a producer of interest, etc.). A circled  2  in  FIG. 13J  shows that a producer C 0 ::I 0 ::ALPHA is instantiated based on the method alpha  1305 . A circled  3  in  FIG. 131  indicates that the shortcut declared producer dependency is processed to determine the producer dependency and the runtime provides the method fly  1376 ; and as a result, a circled  4  indicates that the producer dependency declaration  1374  is accessed. A dashed circled  5  in  FIG. 13J  shows that a producer C 0 ::I 0 ::FLY is instantiated as a dependency determination producer  1380 . A dashed circled  6  in  FIG. 13J  indicates that the producer C 0 ::I 0 ::ALPHA is linked in the producer graph to indicate that producer C 0 ::I 0 ::FLY is a child producer. 
     A circled  7  in  FIG. 13J  indicates that the producer C 0 ::I 0 ::FLY is executed and returns DEP to identify producer  10 . A circled  8  indicates producer  10  is instantiated, while a circled  9  indicates the producer C 0 ::I 0 ::ALPHA being linked in the producer graph to indicate that producer  10  is a child producer. In  FIG. 13J , producer C 0 ::I 0 ::ALPHA and producer  10  are standard producers  1385 . 
     It should be understood that the runtime programmer, in one embodiment of the invention, writes a single fly method to interpret all supported syntaxes and combinations (e.g., the method fly  1334 , the method fly 1   1355 , the method fly 2   1362 , the method fly  1376 ) and includes it in the runtime. This not only allows applications programmers to avoid writing code for dependency determination producers where a fly method may be used, the runtime programmer need only write the generic fly method (the single fly for all supported situations) once. Further, it should be understood that shortcut declared dependencies allow for a runtime that uses dependency determination producers while at the same time allowing an application programmer to indicate standard producers in the producer dependency declarations (e.g.,  FIGS. 13G-J ). 
     Method Tracking Structure 
     Referring back to the method tracking structure of  FIG. 11D , exemplary contents of the ArgumentDependencies column  1194 , FieldDependencies column  1196 , SequencingDependencies column  1195 , UpwardDependencies column  1193 , and WeaklyConstrainedDependencies column  1199  used in some embodiments of the invention will now be described. Specifically, the ArgumentDependencies column  1194  stores a collection of items, one for each ArgumentDependency. In one embodiment of the invention, each item includes the following: 1) the argument ID; 2) a class key nature identifier, being one of explicit class, same class, and contingent class; 3) an explicit class key identifier populated when the class key nature identifier indicates explicit class; 4) contingent class determination method key identifier populated when the class key nature identifier indicates contingent class; 5) an instance key nature identifier, being one of explicit instance, same instance, and contingent instance; 6) an explicit instance key identifier populated when the instance key nature identifier indicates explicit instance; 7) contingent instance determination method key identifier populated when the instance key nature identifier indicates contingent instance; 8) a method key nature identifier, being one of explicit method, same method, and contingent method; 9) an explicit method key identifier populated when the method key nature identifier indicates explicit method; 10) contingent method determination method key identifier populated when the method key nature identifier indicates contingent method; and 11) a shortcut identifier that indicates if the producer dependency declaration for the argument in the producer dependency declaration statement contained an indication of shortcut (i.e., the producer dependency declaration statement directly identifies a standard child producer instead of a dependency determination producer). 
     The “ . . . explicit” indication of the various key nature identifiers is used where the explicit key is provided for the producer dependency in the producer dependency declaration statement. By way of example, the producer dependency “CW::IY::BETA” of the producer dependency declaration statement  1300  of  FIG. 13A  provides an explicit class, instance, and method key. 
     In some embodiments of the invention, a shorthand technique is supported for the producer dependency declaration statements such that: 1) if a class is not provided for a given producer dependency, then the same class as the parent producer is used; and 2) if a class and instance are not provided for a given producer dependency, then the same class and instance as the parent producer are used. In other embodiments of the invention, a syntax is used to allow any combination of class, instance, and method, to be the same as the parent (with the exception of all being the same) (e.g., a separator is used to designate each of class, instance, and method, and an absence of such a separator indicates same as parent—by way of specific example, the syntax may be “#C:”, “#I:”, and “#M:”, such that a producer dependency in a producer dependency declaration statement may be #C:“class key”::#I:“instance key”::#M:“method key”.) (where quotes indicate a placeholder for a value or variable) The “ . . . same” indication of the various key nature identifiers is used where this shorthand technique is used in the producer dependency declaration statement. 
     As previously indicated, in some embodiments of the invention an indication of a contingent producer dependency is supported through a syntax (e.g., &lt;P&gt;) used in the producer dependency declaration statement itself (see  1345  of  FIG. 13G ), and such syntax can be used on one or more of the class, instance, and method of a producer dependency. The “ . . . contingent” indication of the various key nature identifiers is used to identify when such a contingent producer dependency occurs, while the “contingent . . . determination method key identifier” indicates the method key of the child producer (the class and the instance are the same as that of the parent producer). By way of example, the producer dependency “&lt;P&gt;GETC 1 ::I 1 ::M 1 ” for the producer dependency declaration  1345  of  FIG. 13G  provides a contingent class (where the contingent class determination method key is GETC 1 ), an explicit instance key, and an explicit method key. 
     The SequencingDependencies column  1195 , the UpwardDependencies column  1193 , and the WeaklyConstrainedDependencies column  1195  each store a collection of items, one for each SequencingDependency, UpwardDependency, and WeaklyConstrainedDependency. In one embodiment of the invention, each such item has the same structure as an item of the collection for the ArgumentDependencies, except that it does not include an argument ID. Further, although  FIGS. 13A-J  illustrated non-subscription downwardly declared dependencies originating from dependency determination producers, it should be understood that in the case of an upwardly declared dependency or weakly constrained dependency the dependency determination producer may return the other dependencies discussed with reference to  FIG. 7F-G . 
     The FieldDependencies column  1196  stores a collection of items, one for each FieldDependency. While in one embodiment of the invention each item includes the property method key, in alternative embodiments of the invention may have the same structure as an item of the collection from SequencingDependencies. 
     Subscription Dependencies 
     In one embodiment of the invention, both non-subscription and subscription producer dependencies are supported. When a subscription producer dependency is declared for a given method and a given producer is instantiated from that given method, the runtime can resolve during run time (based upon the existence of other producers) the set of zero or more producers that meet the criteria of the subscription. While one embodiment of the invention supports both non-subscription and subscription producer dependencies, alternative embodiments support only non-subscription. In addition, while in one embodiment of the invention two types of subscription dependencies are supported (absorbing and sticky), alternative embodiments of the invention support more, less, and/or different types of subscription producer dependencies. 
       FIGS. 14A-C  are block diagrams illustrating absorbing and sticky subscriptions according to one embodiment of the invention.  FIG. 14A  is a block diagram of an example of the subscription log  1250  of  FIG. 12B  according to one embodiment of the invention. While  FIG. 14A  illustrates this log structure as a table, it should be understood that any suitable data structure may be used (e.g., a hash map).  FIG. 14B  is a block diagram of exemplary producers illustrating a non-contingent, absorbing subscription producer dependency according to one embodiment of the invention.  FIG. 14C  is a block diagram of exemplary producers illustrating a non-contingent, sticky subscription producer dependency according to one embodiment of the invention. Two rows are shown in the table of  FIG. 14A  populated with content used in the examples of  FIGS. 14B-C . Circled numbers are used in  FIGS. 14B-C  to illustrate the order in which operations are performed according to one embodiment of the invention. 
     In  FIG. 14A , a subscriber&#39;s producer key column  1400 , a subscription type column  1405 , and a subscription criteria for trigger producers column  1410  are shown to respectively store the content corresponding to the column name. In addition,  FIG. 14A  shows a parent link modecolumn  1425  to store the link mode for the parent producer of the subscription dependency; this information will be described in more detail with regard to  FIGS. 14B-C . 
       FIG. 14A  also shows a matching producers column  1415  and a completed column  1420  used for absorbing subscriptions. The matching producers column  1415  is used to store the producer keys of the trigger producers that meet the subscription criteria of the absorbing subscription, while the completed column  1420  is used to track whether the absorbing subscription has been completed during a given execution of the current set of producer graphs. The matching producers column  1415  and the completed column  1420  provide an additional optional optimization that allows for the work of scanning the instantiated producers to be divided between the automated producer graph generation and the producer graph execution as described later herein. 
       FIG. 14A  also shows a parent class column  1430 , a parent method column  1435 , and a parent instance column  1437  used for sticky subscriptions. The parent class column  1430 , the parent method column  1435 , and the parent instance column  1437  respectively store the class key, method key, and instance key of the parent producer to be created for the sticky subscription. In addition,  FIG. 14A  shows a dependency determination producer reference column  1421  store a reference to the dependency determination producer creates the subscription. 
     Absorbing Subscription 
     In an absorbing subscription producer dependency, the dependency is to the collection of all producers of the current producer graph structure that meet the absorbing subscription criteria. With reference to  FIG. 14B , a circled  1  indicates a producer  1450  is instantiated (e.g., as a result of designation of the producer  1450  as a producer of interest, as a result of automated discovery of the producer  1450  as a progeny of a producer of interest, etc.). The producer  1450  is based on a method for which the producer dependency declaration includes a producer dependency (e.g., with argument ID X). A circled  2  indicates the producer dependency of the producer  1450  is processed to identify a producer  1455 . 
     A circled  3  indicates that the producer  1450  is linked (in the above example, through argument ID X) in the producer graph to producer  1455  as a child producer. A circled  4  indicates execution of the producer  1455 . The producer  1455  is a dependency determination producer that includes producer dependency declaration code indicating an absorbing subscription producer dependency and indicating the absorbing subscription criteria. As such, the execution of the producer  1455  results in populating the subscription log. With regard to the example in the first row of  FIG. 14A , the subscriber&#39;s producer key column  1400 , the subscription type column  1405 , the subscription criteria for trigger producers column  1410 , the parent link mode column  1425 , and the dependency determination producer reference column  1421  are respectively populated with the producer key of the producer  1450 , an indication that the subscription is of the absorbing type, the absorbing subscription criteria contained within the producer  1455 , the link mode of the producer  1450  linked to the producer  1455  (which, in the case of an absorbing subscription will be an argument dependency and include an argument ID, but whose sticky indicator will indicate not sticky—in the above example, argument ID X), and a reference to the producer  1455  (the dependency determination producer that cerates the subscription). 
     Circled  5 A-N indicates the instantiation of producers  1460 A-N. In this example, the producers  1460 A-N meet the absorbing subscription criteria, and thus are trigger producers. As such, circled  6 A-N indicates the linking of the producer  1450  to the producers  1460 A-N (in the above example, through argument ID X). A circled  7  indicates that the absorbing subscription dependency is completed for the current execution of the producer graph(s), and the producer  1450  is then executed. 
     In one embodiment of the invention, the absorbing subscription criteria can be one or more of any of the keys making up a producer key. Thus, in embodiments of the invention where a producer key comprises a class key, instance key, and a method key, the subscription criteria could be one or more such keys. By way of example with reference to  FIG. 11C , a scan through the instantiated producers for those that meet the subscription criteria is a scan through one or more of the first three columns of the producer graph(s) structure to determine if the keys of the instantiated producers match the keys of the absorbing subscription criteria. While in one embodiment of the invention the absorbing subscription criteria can be one or more of any of the keys making up a producer key, in alternative embodiments of the invention the absorbing subscription criteria is limited to a subset of the keys making up a producer key. 
     Sticky Subscription 
     In a sticky subscription producer dependency, the dependency causes a parent producer to be instantiated for each producer that meets the sticky subscription criteria. With reference to  FIG. 14C , a circled  1  indicates a producer  1470  is instantiated (e.g., as a result of designation of the producer  1470  as a producer of interest, as a result of automated discovery of the producer  1470  as a progeny of a producer of interest through a sequencing dependency (e.g., as a result of a SequencingDependency or WeaklyConstrainedDependency, etc.). The producer  1470  is a dependency determination producer that includes producer dependency declaration code indicating a sticky subscription, the sticky subscription criteria for the trigger producers, and the sticky subscription characteristics for the parent producer to be created. 
     Execution of the producer  1470  results in populating the subscription log. With regard to the example in the second row of  FIG. 14A , the subscriber&#39;s producer key column  1400 , the subscription type column  1405 , and the subscription criteria for trigger producers column  1410  are respectively populated with the producer key of the producer  1470 , an indication that the subscription is of the sticky type, and the sticky subscription criteria for the trigger producers contained within the producer  1470 . In addition, the parent class column  1430 , the parent method column  1435 , the parent instance column  1437 , and the link mode column  1425  of the parent producer to be linked to the trigger producer are populated with the sticky subscription characteristics for the parent producer to be created—in this embodiment of the invention, respectively the class of the parent producer to be instantiated, the method of the parent producer to be instantiated, the instance of the parent producer to be instantiated (if left blank, would be equal to the instance key of the trigger producer), the link mode (which, in the case of sticky subscription, may be: 1) argument, field, or sequencing dependency; 2) argument ID if an argument dependency—the argument ID of the parent producer to be linked to the trigger producer (e.g., argument ID Y). In addition, the dependency determination producer reference column  1421  is populated with a reference to the dependency determination producer that created the subscription (in  FIG. 14C , the producer  1470 ). 
     With reference to  FIG. 14C , a circled  2  indicates a producer  1475  is instantiated (e.g., as a result of designation of the producer  1475  as a producer of interest, as a result of automated discovery of the producer  1475  as a progeny of a producer of interest, etc.). In addition, it is determined if the producer  1475  meets the sticky subscription criteria for a trigger producer. A circled  3  indicates that responsive to the trigger producer  1475 , a producer  1480  is instantiated based on the sticky subscription characteristics for the parent producer to be created. With reference to the exemplary second row of  FIG. 14C , the class key, method key, instance key, and link mode are accessed from the parent class column  1430 , the parent method column  1435 , the instance column  1437 , and the parent link mode column  1425 , respectively. The parent producer has a producer key comprising the accessed class key, the accessed instance key (if left blank, the instance key of the trigger producer (in  FIG. 14C , the producer  1475 )), and the accessed method key—in the example of  FIG. 14C , this is producer  1480 . A circled  4  indicates that the instantiated parent producer  1480  is linked in the producer graph to the child trigger producer  1475  through the accessed link mode (in the above example, link mode type=argument dependency; link mode argument ID=Y). Also at circled  4 , in the case of an argument dependency, the sticky indicator is set to indicate sticky—that the producer dependency in that position of the producer dependency declaration statement for the method on which the instantiated parent producer  1480  is based should be ignored for the producer  1480 —this prevents the link created by the sticky subscription producer dependency from being overwritten by later automated producer graph generation operations 
     In one embodiment of the invention, the sticky subscription criteria for trigger producers can be one or more of the keys making up a producer key. Thus, in embodiments where a producer key comprises a class key, instance key, and a method key, the sticky subscription criteria for the trigger could be one or more of the class, instance, and method keys. By way of example with reference to  FIG. 11C , a scan through the instantiated producers for those that meet the sticky subscription criteria for trigger producers is a scan through one or more of the first to third columns of the producer graph(s) structure to determine if the keys of the instantiated producers match the keys of the sticky subscription criteria for trigger producers. While in one embodiment of the invention the sticky subscription criteria for trigger producers can be one or more of the keys making up a producer key, in alternative embodiments of the invention the absorbing subscription criteria can be a more limited number of the keys making up a producer key. 
       FIGS. 14D-E  illustrate the choice of a parent producer based upon a parent dependency determination producer according to one embodiment of the invention. While  FIGS. 14D-E  are described with reference to argument dependencies, embodiments of the invention may support the use of sequencing and field dependencies. 
       FIG. 14D  illustrates the choice of a parent producer based upon a parent dependency determination producer created by a sticky subscription according to one embodiment of the invention. Like  FIG. 14C ,  FIG. 14D  shows the sticky subscription producer  1470  and the trigger producer  1475 ; however, rather than the producer  1480 ,  FIG. 14D  shows a dependency determination producer  1480  created through the sticky subscription of sticky subscription producer  1470 . Further,  FIG. 14D  shows that the link mode of the sticky subscription is argument dependency, argument ID=X, and sticky indicator=sticky. As illustrated by the dashed curved line from the producer  1475  to the dependency determination producer  1480 , the DEP returned by the dependency determination producer may be based on the output of the producer  1475  itself (the argument of argument ID=X). In  FIG. 14D , the dependency determination producer  1480  returns an non-subscription upwardly declared producer dependency on a producer  1482 , with the link mode indicating argument dependency and argument ID=Y. While the argument IDs of X and Y are used in  FIG. 14D  to show that they may differ, it should be understood that they may be equal. 
       FIG. 14E  illustrates the choice of a parent producer based upon a parent dependency determination producer created by a child dependency determination producer, which child dependency determination producer is linked by a sequencing dependency, according to one embodiment of the invention.  FIG. 14E  is similar in structure to  FIG. 14D ; specifically, the producer  1475 ,  1480 , and  1482  are replaced with producers  1486 ,  1496 , and  1498 . However, rather than the sticky subscription producer  1470  creating the link between the producers  1480  and  1475 , the producer  1486  has a sequencing dependency on a dependency determination producer  1494  (e.g., created through an UpwardDependency or a WeaklyConstrainedDependency), which creates the dependency determination producer  1496  through a non-subscription upwardly declared dependency. 
     It is worth nothing that sticky subscriptions and non-subscription upwardly declared dependencies (e.g., created through UpwardDependencies and/or WeaklyConstrainedDependencies) cause a bottom up building of a producer graph (as opposed to the top down building described earlier herein). Further, this bottom up building is not limited to the building of a single level, but may be multiple level (e.g., if, due to a sticky subscription or non-subscription upwardly declared dependency, a parent producer is instantiated, that same parent producer may also be a trigger producer for a sticky subscription or may include a non-subscription upwardly declared dependency and cause the instantiation of another parent producer, and so on). In this sense, sticky subscriptions, as well as non-subscription upwardly declared dependencies, reverse producer graph building. 
     While in some embodiments of the invention the parent producers identified by the sticky subscription characteristics are standard producers (see  FIG. 14C ), alternative embodiments may be implemented to support the identification of other types of producers. For example, in embodiments of the invention that allow the sticky subscription characteristics to identify a dependency determination producer (see  FIG. 14D ), such a dependency determination producer may access the output of the trigger producer and may, based on that output, trigger the creation of a particular producer as a parent producer that needs to stick on the child (this parent producer might already exist or not; If it already exists, it is simply linked, and the child producer is added to its argument; If is does not exist yet, it is created). The case where the dependency determination producer returns a constant producer mimics an absorbing subscription. The case where the dependency determination producer returns a producer whose instance key is unique per trigger producer (e.g., returns a producer whose instance key is the producer key of the trigger producer) results in a separate parent producer per child producer and is referred to as a pure sticky subscription. The case where the dependency determination producer returns an instance key which is neither constant nor unique per trigger producer can mix the behaviors of pure sticky subscriptions and absorbing subscriptions and is referred to as a non-pure sticky subscription. 
     Exemplary Advantages 
     As previously described, in one embodiment of the invention, producer dependencies are declared for methods as a way to specify method invocation sequencing using the appropriate instances (where the appropriate instances include the instances to use as arguments, the instances to be used by instance methods, and the meta class instances used by class methods) without using manual invocation sequencing code; effectively, the work of generating some or all of manual invocation sequencing code is replaced with: 1) work done by the application programmer to write the producer dependency declarations; and 2) work done by the runtime to discover and build the producer graph(s) and execute the producers of that producer graph(s). Although the effort to write the runtime is relatively great, it needs only be written once in that it can be used to execute any object-oriented applications written for the runtime; in contrast, for a typical application, the effort to write the producer dependency declarations is relatively low in comparison to writing manual invocation sequencing code. 
     Non-dynamic producer dependencies provide for a way to specify unconditional method invocation sequencing code, and thus avoid the need for writing unconditional manual invocation sequencing code. Contingent producer dependencies provide for a way to specify conditional processing, and thus replace the need for writing conditional manual invocation sequencing code. Supporting producer dependencies that allow for a collection of producers to be returned provides for a way to specify the filling of a collection before it is passed as a parameter, and thus avoid the need for writing multiple calls in manual invocation sequencing code to fill a collection before it is passed as a parameter. Supporting subscriptions provides an environment in which a programmer need not write specific listening code for each type of object to be listened to (e.g., in a producer graph oriented programming spreadsheet, an absorbing subscription may be used to compute an average of a range of cells (each cell being a producer) by having the absorbing subscription criteria identify cells within the range, and re-computing the average every time a new producer is added to the absorbing subscription; in a producer graph oriented programming spreadsheet, a sticky subscription may be used as a currency converter by having the sticky subscription criteria identify cells holding currency content and sticky subscription characteristics of sticky producer(s) to be instantiated that perform currency conversion (the producers (holding the converted amounts) created by the sticky subscriptions would then be available for display in other cells). 
     Operation 
     New Instance Commands 
       FIG. 15  is a flow diagram for instantiating new instances according to one embodiment of the invention. As previously described with reference to  FIG. 10 , the new class module  1095  of  FIG. 10  may be implemented as part of the new instance module  1098 . The flow diagram of  FIG. 15  assumes such an embodiment and is performed by the new instance module  1098 ; the part of the flow diagram of  FIG. 15  representing the new class module  1095  is shown as the dashed block  1580 , which includes blocks  1540  and  1550 . 
     Responsive to a new instance command (block  1510 ), control passes to block  1520 . In block  1520 , it is determined if the instance already exists. If not, control passes to block  1530 , otherwise, the instance need not be instantiated and control passes to block  1570  in which the flow diagram ends. In one embodiment that supports instance keys, block  1520  is performed by accessing the instance tracking structure  1065  of  FIG. 10  for the instance key (and class key if instance keys need not be unique across classes) provided as part of the new instance command. 
     In block  1530 , it is determined if the class definition of the instance is already loaded. If not, control passes to block  1540 ; otherwise, control passes to block  1560 . In one embodiment that supports class keys, block  1540  is performed by accessing the class tracking structure  1092  of  FIG. 10  for the class key provided as part of the new instance command. 
     In block  1540 , the class is loaded and control passes to block  1550 . In block  1550 , the class definition would be stored according to the class key and introspected, including any producer dependency declaration statements (stored by method key within the class—see  FIG. 11D ). From block  1550 , control passes to block  1560 . With reference to  FIG. 10 , the following is performed in blocks  1540  and  1550 : 1) the class would be loaded from the class definitions that include business logic  1010  into the classes  1054  (this loading results in the methods and producer dependency declarations of the class being stored in the method and producer dependency declarations  1056 ); 2) the class would be added to the class tracking structure  1092 ; and 3) the methods would be added to the method tracking structure  1058 . Further, the output classes of the methods would be loaded. 
     In block  1560 , an instance of the class would be instantiated and stored according to the instance key. With reference to  FIG. 10 , the instance would be instantiated into the instances  1052 ; and the instance would be added to the instance tracking structure  1065 . From block  1550 , control passes to block  1570  in which the flow diagram ends. In some embodiments of the invention in which an object-relational mapping technique is used, data may be loaded from an external data source to populate the field of the instance as part of block  1560 . 
     In some embodiments of the invention, classes and instances may be loaded/instantiated in a manner in which the runtime with producer graph oriented programming support is not aware (e.g., in  FIG. 9A , if the runtime  915  loads/instantiates without runtime  910  being aware). In such cases, embodiments of the invention which also support the instance key being an instance of the class InstanceKey (which holds two elements: an instance key nature indicating if the key identifier is a reference to the instance or another object (such as a string), and a key identifier which can either be a reference to the instance, or another object (such as a string)), blocks  1520  and  1530  inquire whether the instance and class were instantiated/loaded in a manner in which the runtime with producer graph oriented programming support is aware. In cases where the runtime with producer graph oriented programming support is not aware of an already loaded class, the class would not be loaded, but the class would be added to the class tracking structure  1092  and the methods would be added to the method tracking structure  1058 . In cases where the runtime with producer graph oriented programming support is not aware of an already instantiated instance, the instance would not be instantiated, but the instance would be added to the instance tracking structure  1065 . 
     New Producer and Unoverride Commands 
       FIG. 16A  is a flow diagram for instantiating new producers and unoverriding producers according to one embodiment of the invention. With reference to  FIG. 10 , the flows of  FIG. 16A  are performed by the automated producer graph generation module  1040  and the override producer module  1045  (or, as described with reference to alternative embodiments regarding  FIG. 10 , the module that handles overrides and unoverrides). 
     Responsive to a new producer command (block  1600 ), control passes to block  1605 . In one embodiment of the invention, a new producer command may execute responsive to a variety of situations. Table 2 below identifies the various situations and parameters passed according to one embodiment of the invention. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                   
                   
                   
                 Dependency 
               
               
                   
                   
                 Called Producer (to 
                   
                   
                 determination 
               
               
                   
                 Caller 
                 be created if does 
                   
                   
                 producer 
               
               
                 Situations 
                 Producer 
                 not already exist) 
                 Call type 
                 Link mode 
                 reference 
               
               
                   
               
             
            
               
                 Producer of 
                 N/A 
                 Producer of interest 
                 Of interest 
                 N/A 
                 N/A 
               
               
                 interest 
                   
                 to be created 
                   
                   
                   
               
               
                 Non- 
                 Parent 
                 Child 
                 Non- 
                 Caller parent 
                 Dependency 
               
               
                 subscription 
                   
                   
                 subscription 
                 producer link 
                 determination 
               
               
                 downwardly 
                   
                   
                 downwardly 
                 mode 
                 producer 
               
               
                 declared 
                   
                   
                 declared 
                   
                 providing the 
               
               
                   
                   
                   
                   
                   
                 dependency 
               
               
                 Sticky 
                 Child 
                 Parent (parent 
                 Sticky 
                 Called parent 
                 Dependency 
               
               
                 subscription 
                   
                 class, method, and 
                   
                 producer link 
                 determination 
               
               
                   
                   
                 instance key from 
                   
                 mode from sticky 
                 producer 
               
               
                   
                   
                 sticky subscription 
                   
                 subscription 
                 providing the 
               
               
                   
                   
                 characteristics for 
                   
                 characteristics for 
                 dependency 
               
               
                   
                   
                 parent producer to 
                   
                 parent producer 
                   
               
               
                   
                   
                 be created; if 
                   
                 to be created 
                   
               
               
                   
                   
                 instance key is 
                   
                   
                   
               
               
                   
                   
                 blank, instance key 
                   
                   
                   
               
               
                   
                   
                 of existing child 
                   
                   
                   
               
               
                   
                   
                 caller producer) 
                   
                   
                   
               
               
                 Override 
                 N/A 
                 Producer to be 
                 Overridden 
                 N/A 
                 N/A 
               
               
                   
                   
                 overridden 
                   
                   
                   
               
               
                 Non- 
                 Child 
                 Parent 
                 Non- 
                 Called parent 
                 Dependency 
               
               
                 subscription 
                   
                   
                 subscription 
                 producer link 
                 determination 
               
               
                 upwardly 
                   
                   
                 upwardly 
                 mode 
                 producer 
               
               
                 declared 
                   
                   
                 declared 
                   
                 providing the 
               
               
                   
                   
                   
                   
                   
                 dependency 
               
               
                   
               
            
           
         
       
     
     In block  1605 , it is determined if the producer already exists. If not, control passes to block  1610 ; otherwise, control passes to block  1670 . Block  1605  is performed by accessing a class, instance, and method identified (e.g., by key and/or reference) as part of the new producer command. In one embodiment that supports producer keys, block  1605  is performed by accessing the producer graph(s) structure  1060  of  FIG. 10  for the producer key provided as part of the new producer command (the producer key in the called producer column of Table 2). 
     In block  1610 , the new instance module is called with a new instance command and control passes to block  1615 . In one embodiment of the invention, block  1610  is performed by calling the flow diagram of  FIG. 15  using the instance key from the producer key in the called producer column of Table 2. 
     In block  1615 , the class definition of the instance of the producer is accessed and control passes to block  1620 . With reference to  FIG. 10 , block  1615  is performed by using the class key from the producer key in the called producer column of Table 2 to access the appropriate one of the classes  1054  according to the class tracking structure  1092 . 
     In block  1620 , the method and producer dependency declaration statement of the producer is accessed and control passes to block  1623 . With reference to  FIG. 10 , block  1620  is performed by using the method key from the producer key in the called producer column of Table 2 to access the appropriate one of the methods and producer dependency declarations  1056  from the class located in block  1615 . 
     In block  1623 , the producer execution mode is determined and control passes to block  1625 . Details of one exemplary manner in which block  1623  is performed are discussed below. In some embodiments, a default execution mode is defined as an annotation at code level. The behavior may be overridden at run time by the end user or by the client code through a producer-based configurable decision structure (e.g., the producer based configurable decision structure  1049  in  FIG. 10 ) on a class basis, a method basis, an instance basis, or any combination of the above. Moreover, runtime settings may be provided to enable the runtime to ignore these programming annotations or user-defined configurations by forcing execution to be performed in a predetermined execution mode, depending on the computing environment (e.g., availability of several processors on a single machine, grid availability, load of processor(s), etc.). 
     In block  1625 , the producer is added to the producer graph and control passes to block  1630 . With reference to the embodiment of the invention in  FIG. 11C , the first three columns are populated. 
     In block  1630 , for each registered subscription, the subscription filtering criteria is processed to determine if the producer matches. With reference to the embodiment of the invention in  FIG. 14A , a subscription is considered registered when it is added to the subscription log. Exemplary operations to register subscription are described later herein. Block  1630  is an optional optimization that allows for the work of scanning the instantiated producers to be divided between automated producer graph generation and producer graph execution. As such, an alternative embodiment of the invention may not perform block  1630 . 
     In block  1635 , the producer is linked into the producer graph(s) if called due to a dependency. From block  1635 , control passes to block  1640 . The manner of performing block  1635  depends on the situation which resulted in the new producer command being executed. For example, if the situation is that this is a producer of interest or a producer being overridden, then it was not called due to a dependency and nothing is done. In contrast, if the situation is non-subscription downwardly declared, then it was called due to a non-subscription downwardly declared dependency; and with reference to the embodiment of the invention in  FIG. 11C , the following is performed: 1) the parent producer(s) link(s) in column  1150  of the called child producer (the called producer column of table 2) is modified with a parent producer reference to the row of the parent caller producer (the caller producer column of table 2); and the dependency determination producer reference (the dependency determination producer reference column of Table 2); and; 2) the child producer(s) link(s) column  1160  of the row of the parent caller producer (the caller producer column of table 2) is modified with a child producer reference to the row of the called child producer (the called producer column of Table 2), a dependency determination producer reference (the dependency determination producer reference column of Table 2), and a link mode (set according to the link mode column of Table 2). 
     In contrast, if the situation is a sticky subscription, then it was called due to a trigger producer being identified; and with reference to the embodiment of the invention in  FIG. 11C , the following is performed: 1) the parent producer(s) links(s) column  1150  of the caller child producer (the caller producer column of table 2) is modified with a parent producer reference to the row of the parent called producer (the called producer column of table 2) and the determination dependency producer reference (the dependency determination producer reference column of Table 2); and 2) the child producer(s) link(s) column  1160  of the row of the parent called producer (the called producer column of table 2) is modified with a child producer reference to the row of the caller child producer (the caller producer column of Table 2); 2) a dependency determination producer reference (the dependency determination producer reference column of Table 2), a link mode (set according to the link mode column of Table 2) and a sticky indicator set to indicate sticky. In this respect, the situation of a non-subscription upwardly declared dependency is handled in a similar fashion to sticky subscription. 
     In block  1640 , the producer is marked as unexecuted and control passes to block  1645 . With reference to the embodiment of the invention in  FIG. 11C , the incremental execution marking column  1180  of the appropriate row is populated with an unexecuted indication. 
     In block  1645 , it is determined if the producer has any dependencies and is not overridden. If so, control passes to block  1650 ; otherwise, control passes to block  1665 . Block  1645  is performed by checking the producer dependency declaration accessed in block  1620  and the call type column of Table 2. 
     In block  1650 , for each dependency in the producer dependency declaration that is to be resolved now, the number of producers is determined and a new producer command is invoked for each. From block  1650 , control passes to block  1655 . Different embodiments of the invention determine different types of dependency at different times; the manner of performing block  1650  in one exemplary embodiment of the invention will be described later herein. 
     In block  1655  the producer is added to the execution start log if all its dependent producers exist and have been executed. From block  1655 , control passes to block  1660 . When, for a given producer instantiated as part of the current iteration of this flow, block  1655  is performed, then the invocation of another iteration of this flow for a dependent producer will return the execution status of the producer (see block  1660 ) (e.g., with regard to the embodiment of the invention of  FIG. 11C , the status from the incremental execution marking column  1180  of the appropriate row(s)). If all the dependent producer(s) exist and the execution status of all of the dependent producers is executed, then the producer of the current iteration is added to the execution start log. 
     In block  1660 , the execution status of the producer is returned as a parameter. 
     In block  1665 , the producer is added to the execution start log and control passes to block  1660 . 
     In block  1670 , similar to block  1635 , the producer is linked into the producer graph(s) if called due to a dependency. From block  1670 , control passes to block  1675 . Block  1670  may be reached for a variety of reasons. For example, block  1670  may be reached because the producer was previously instantiated responsive to a producer override command, but not linked into the producer graph. As another example, block  1670  may be reached because the producer is already part of a producer graph and is being added to another (e.g., previously instantiated responsive to being a producer of interest, a progeny of a producer of interest, etc.). 
     In block  1675 , it is determined if the new producer flow is called due to an override, to a sticky subscription dependency, or a non-subscription upwardly declared dependency. If so, control passes to block  1680 ; otherwise, control passes to block  1660 . Block  1675  is performed by checking the call type column of Table 2 to see if this is a call for an overridden producer, a sticky subscription dependency, or a non-subscription upwardly declared dependency. 
     In block  1680 , similar to block  1640 , the producer is marked as unexecuted and control passes to block  1665 . Block  1680  may be reached for a variety of reasons. 
     Responsive to a producer unoverride command (block  1690 ), control passes to block  1695 . In block  1695 , the producer is marked as not overridden and control passes to block  1640 . With reference to the embodiment of the invention of  FIG. 11C , the producer output caching and override producer output indications column  1170  of the row of the producer are accessed and altered to indicate that the producer is no longer overridden. Continuing this flow, block  1640  would lead to block  1645 , and if the producer had any dependencies, to block  1650 , which would cause the producer graph under the producer to be discovered and built if it was not already. If the producer graph under the producer is already discovered and built, then the invoking of the new producer command will result in flows going from  1600 , to  1605 , to  1670 , and so on; further, the returning of the execution status of the producers of the graph under the producer in block  1660  will determine if the producer is added to the execution start log in block  1655 . However, if the producer graph under the producer is not discovered and built, then the invoking of the new producer command will result in it being discovered and build with flows going from  1600 , to  1605 , to  1610 , and so on. 
       FIG. 16B  is a flow diagram for block  1623  of  FIG. 16A  according to one embodiment of the invention. Thus, control flows from block  1620  to block  16231  in block  1623 . In block  16231 , a runtime execution setting override is checked. Then it is determined if the runtime execution setting override is enabled at block  16233 . If it is set, then the execution mode is set according to the runtime execution setting at block  16234 . Otherwise, the producer-based configurable decision structure for execution mode selection from end user is checked in block  16235  and control passes to block  16236 . At block  16236 , it is determined if the end user has made any execution mode selection. If yes, then the execution mode is set according to the setting in the producer-based configurable decision structure at block  16237 . Otherwise, the method definition of the producer is checked for execution mode defined as an annotation at code level and the execution mode is set according to the annotation at block  16238 . From block  16238  or block  16237 , control passes to block  16239  to end the process within block  1623 . 
       FIG. 17  is a flow diagram for block  1650  of  FIG. 16  according to one embodiment of the invention. Thus, control flows from block  1645  to block  1700  in block  1650 . In block  1700 , for each dependency in the producer dependency declaration of the producer (one for each ArgumentDependency, FieldDependency, SequencingDependency, UpwardDependency, and WeaklyConstrainedDependency), the following blocks  1705 - 1745  are performed. With reference to the  FIGS. 10 and 11D , the method tracking structure is accessed to determine information regarding the producer dependency. It should also be understood that blocks  1715 ,  1725 ,  1730 ,  1740 ,  1745 , and  1750  are an optimization when performed prior to execution of the producer graph. 
     In block  1705 , it is determined if the dependency is an argument dependency linked already due to a sticky dependency. If so, control passes to block  1710  where the flow is complete for this dependency; otherwise, control passes to block  1715 . With regard to the embodiment of the invention show in  FIG. 11C , the sticky indicator is checked to determine if the argument ID of this dependency is subject to a sticky subscription argument dependency or an upwardly declared argument dependency. 
     In block  1715 , it is determined if the dependency is a contingent dependency. If so, control passes to block  1720 ; otherwise, control passes to block  1725 . Block  1715  is performed by checking the producer dependency declaration of the child producer identified by the dependency to determine if it is empty (the child producer is and independent producer). With regard to  FIGS. 13A-J , this would be true for producers with dashed circled numbers (e.g., in  FIG. 13D , producer CU::IV::DELTA), but not true for the other producers (e.g., in  FIG. 13D , producer CW::IY::BETA). Thus, with reference to  FIG. 13D , block  1715  is represented by circled  1 ,  4 , and  8 . Block  1715  and the flow from it through blocks  1725 - 1750  is an optimization that both avoid adding/linking the producers with dashed circled numbers to the producer graph, as well as dividing the work of executing producers between the automated producer graph generation and producer graph execution. 
     In block  1720 , a new producer command for the dependency determination producer is invoked and the flow ends. For example, with reference to  FIG. 13D , block  1720  causes what is represented by circled  5 ,  6 , and  7 . 
     In block  1725 , the dependency determination producer is executed and control passes to block  1730 . For example, with reference to  FIG. 13D , block  1725  is represented by circled  11  (thus, the flow of  FIG. 17  illustrated the previously described embodiment in which circled  9  and  10  of  FIG. 13D  are not performed). 
     In block  1730 , it is determined if the dependency is a non-subscription dependency. If so, control passes to block  1750 ; otherwise control passes to block  1740 . In other words, in block  1725 , the producer dependency determination code in the method of the dependency determination producer, which is part of the producer dependency declaration of the parent producer, is executed. Having executed this producer dependency declaration code, which code would identify if this dependency is a subscription dependency, the type of producer dependency of the parent producer is determined. With regard to the example in  FIG. 13D , circled  11  would result in the flow of  FIG. 17  passing from block  1730  to block  1750 . 
     In block  1750 , the number of producers returned by the execution of the dependency determination producer in block  1725  is determined and a new producer command is invoked for each, using the arguments described in Table 2, including the dependency determination producer reference executed in  1725 . For example, with reference to  FIG. 13D , block  1750  would cause circled  12  and  13  and circled C and D. 
     With reference to the absorbing subscription example of  FIG. 14B , block  1725  represents circled  4 ; which causes the flow to pass through block  1730  to block  1740 . 
     In block  1740 , the subscription is added to the subscription log, and if the subscription is absorbing, it is marked as incomplete. From block  1740 , control passes to block  1745 . With reference to the embodiment of the invention shown in  FIG. 14A , the subscription log is populated with the subscription as previously described. 
     In block  1745 , all of the instantiated producers are scanned to see if they match the criteria of the subscription (and thus are a trigger producer), and any matches are processed. 
       FIG. 18  is a flow diagram for block  1745  of  FIG. 17  according to one embodiment of the invention. Thus, control flows from block  1740  to block  1800  in block  1745 . In block  1800 , for each instantiated producer, the following blocks  1810 - 1830  are performed. 
     In block  1810 , it is determined if the producer meets the criteria of the subscription. If so, control passes to block  1815 ; otherwise, control passes to block  1830  where the flow ends for the producer currently being processed. With reference to the embodiments of the invention shown in  FIGS. 11C and 14A , the producer graph(s) are accessed to determine whether they include producers that meet the criteria of the subscription. 
     The manner of processing a matching producer depends on the type of subscription being processed. With reference to block  1815 , if the subscription is of the absorbing type, control passes to block  1825 ; otherwise, control passes to block  1820 . Block  1815  would be performed responsive to the type of subscription added in  1740  or  2235 . 
     In block  1825 , the matching producer is added to the subscription log and the producer with the absorbing subscription is linked to the matching producer. From block  1825 , control passes to block  1830 . With reference to the embodiments of the invention shown in  FIGS. 11C and 14A -B, the following is performed: 1) the subscription criteria from the subscription criteria for trigger producers column  1410  was used in block  1810  and a matching producer was located (e.g., one of producer  1460 A-N); 2) the matching producer is added to the matching producer column  1415  at the row of the subscription; and 3) the producer with the absorbing subscription (e.g., producer  1450 ) is linked to the matching producer (e.g., the one of the producers  1460 A-N) in the producer graph(s) structure of  FIG. 11C  (using the dependency determination producer reference extracted from the dependency determination producer reference column  1421  of the subscription log  14 A for the given absorbing subscription. 
     In block  1820 , a new producer command is invoked for the parent producer to be created. From block  1820 , control passes to block  1830  where the flow diagram ends for the current produced selected in block  1800 . With reference to the embodiments of the invention shown in  FIGS. 14A and 14C , the following is performed: 1) the subscription criteria from the subscription criteria for trigger producers column  1410  was used in block  1810  and a matching producer was located (e.g., producer  1475 ); and 2) a new producer command is invoked with the parameters of table 2 set as follows: a) call type is sticky subscription; b) caller producer is the producer key of the caller child producer (e.g., producer  1475 ); c) called producer is the producer key of the called parent producer to be created (e.g., producer  1480 ), that producer key being formed using the parent class, instance, and method key from the sticky subscription characteristics for the parent producer to be created ( FIG. 14A , columns  1430  and  1435  and  1437  (if the instance key is empty, the instance key of caller child producer is used); and d) the link mode for the called parent producer (figured  14 A, link mode in column  1425 , and e) the dependency determination producer reference extracted from the dependency determination producer reference column  1421  of subscription log  14 A for the given sticky subscription. 
       FIG. 19  is a flow diagram for block  1630  of  FIG. 16  according to one embodiment of the invention. Thus, control flows from block  1625  to block  1900  in block  1630 .  FIG. 19  is very similar to  FIG. 18 . Specifically, blocks  1910 ,  1915 ,  1920 , and  1930  of  FIG. 19  are identical to blocks  1810 ,  1815 ,  1820 , and  1830 ; while block  1900  and  1925  differ from blocks  1800  and  1825 . As such, only the difference will be described here. 
     Block  1900  indicates the flow is performed for each registered subscription, whereas block  1800  indicates the flow is performed for each instantiated producer. Thus, where the flow of  FIG. 18  is centered on a single subscription and scanning all producers, the flow of  FIG. 19  is centered on a single producer and scanning all subscriptions. 
     Block  1925  is the same as block  1825 , with the exception that the absorbing subscription is marked as incomplete. With reference to the embodiment of the invention shown in  FIG. 14A , the completed column  1420  at the appropriate row is updated to indicate incomplete. 
       FIG. 20  is a flow diagram for blocks  1635  and  1670  of  FIG. 16  according to one embodiment of the invention. Thus, control flows from block  1605  and block  1630  to block  2005  in blocks  1635  and  1670 . In block  2005 , it is determined if this iteration of the flow diagram of  FIG. 16  was invoked due to a dependency (e.g., from block  1630  (block  1920 ) or  1650  (blocks  1720 ,  1750  or  1745 / 1820 ) of a prior iteration). If not, control passes to block  1640  or  1675  depending from where the flow was entered (from block  1630  or  1605 ). 
     In block  2010 , it is determined if the flow was called due to a sticky subscription or non-subscription upwardly declared situation. If not, control passes to block  2015 ; otherwise, control passes to block  2020 . Block  2010  is performed by checking the call type parameter from Table 2 (i.e., whether the call type is sticky subscription or non-subscription upwardly declared or not). With reference to the embodiments of the invention shown in  FIGS. 18 and 19 , if the new producer command was invoked from blocks  1820  or  1920 . 
     In block  2020 , the current parent producer is linked to the caller child producer. With reference to the embodiments of the invention shown in  FIGS. 11C and 14C , the called parent producer (e.g., producer  1480 ) identified by the parameter from the called producer column of table 2 is linked in the producer graph(s) structure of  FIG. 11C  to the caller child producer (e.g., producer  1475 ) identified by the parameter from the caller producer column of table 2, using the link mode and dependency determination producer reference identified by the parameter from the link mode and dependency determination producer reference columns of Table 2. If the parent existed previously, the behavior of block  2020  mimics the behavior of an absorbing subscription dependency in the sense that a single argument can be mapped to zero or more child producers. 
     In block  2015 , the caller parent producer is linked to the current called child producer. With reference to the embodiment of the invention shown in  FIG. 11C , the caller parent producer identified by the parameter from the caller producer column of table 2 is linked in the producer graph(s) structure of  FIG. 11C  to the called child producer identified by the parameter from the called producer column of table 2, using the dependency determination producer reference identified by the dependency determination producer reference column of Table 2. From blocks  2015  and  2020 , control passes to block  1640  or  1675  depending for where the flow was entered (from block  1605  or  1630 ). 
       FIG. 21A  is a flow diagram for overriding producers according to one embodiment of the invention. With reference to  FIG. 10 , the flow of  FIG. 21A  is performed by the override producer module  1045  (or, as described with reference to alternative embodiments regarding  FIG. 10 , the module that handles overrides and unoverrides). 
     Responsive to an override producer command (block  2110 ), control passes to block  2120 . In block  2120 , a new producer command is invoked for the producer identified by the override producer command and control passes to block  2130 . Block  2120  is performed in one embodiment of the invention in case the producer to be overridden has not yet been instantiated, as well as to mark the producer as unexecuted (block  1640  or  1680 ) and log it on the execution start log (block  1665 ). An alternative embodiment of the invention that does not allow the overriding of a producer that is not yet instantiated would perform an additional check between blocks  1605  and  1610  to determine if this new producer command was called responsive to an override producer command, and to indicate an error if this new producer command was called responsive to an override producer command. 
     In block  2130 , the output in the producer output cache (and in the instance if a field) is set and the producer is marked as overridden. 
       FIG. 21B  is a flow diagram for overriding producer execution modes according to one embodiment of the invention. With reference to  FIG. 10 , the flow of  FIG. 21B  is performed by the parallelization module  1076  (or, as described with reference to alternative embodiments regarding  FIG. 10 , the module that handles parallelization). 
     Responsive to an override execution mode command (block  2150 ), control passes to block  2155 . In block  2155 , the producer execution mode setting is overridden in the producer graph structure  1060 . 
       FIG. 21C  is a flow diagram for overriding producer execution modes according to one embodiment of the invention. With reference to  FIG. 10 , the flow of  FIG. 21C  is performed by the parallelization module  1076  (or, as described with reference to alternative embodiments regarding  FIG. 10 , the module that handles parallelization). 
     Responsive to a runtime execution mode setting override command (block  2160 ), control passes to block  2165 . In block  2165 , the producer execution mode setting is overridden globally in the runtime setting structure  1048 . 
       FIG. 21D  is a flow diagram for overriding producer execution modes according to one embodiment of the invention. With reference to  FIG. 10 , the flow of  FIG. 21D  is performed by the parallelization module  1076  (or, as described with reference to alternative embodiments regarding  FIG. 10 , the module that handles parallelization). 
     Responsive to a configurable execution mode decision structure override producer command (block  2170 ), control passes to block  2175 . In block  2175 , the producer execution mode setting is overridden globally in the producer-based configurable decision structure on a class basis, a method basis, an instance basis, or a combination of any of the above. 
     Global Execute Commands 
       FIG. 22A  is a part of a flow diagram for execution of the current producer graph(s) according to one embodiment of the invention; while  FIG. 22B  is another part of a flow diagram for execution of the current producer graph(s) according to one embodiment of the invention. With reference to  FIG. 10 , the flow of  FIG. 22  is performed by the producer graph execution module  1070 . 
     Responsive to a global execute command, block  2200  shows that a set of candidate producers is selected to be executed based on the producers on the execution start log and control passes to block  2205 . In one embodiment of the invention the overridden producers are marked as unexecuted and execution thereof returns their overridden result (as opposed to causing their method to be executed), the current set of candidate producers is the producers on the execution start log. While one embodiment of the invention is described above in which overridden producers are marked as unexecuted and execution thereof returns their overridden result (as opposed to causing their method to be executed), alternative embodiments may operate differently (e.g., mark overridden producers as executed and when selecting the current set of candidate producers, the independent producers of the execution start log and the parents of overridden producers on the execution start log are selected). 
     In block  2205 , a subset of producers ready for execution is selected from the set of candidate producers and control passes to block  2207 . An exemplary manner of performing block  2205  is described later herein. 
     In block  2207 , the producers in the current set of ready producers are executed with parallelization if parallelization is enabled. An exemplary manner of performing block  2207  is described later herein. Control passes from block  2207  to block  2208  afterwards. 
     In block  2208 , a task is read and removed from one of the result task queues of the supported execution modes. In the current examples, the result task queues include MP_RESULT_TASK_QUEUE, MT_RESULT_TASK_QUEUE, and LOCAL_RESULT_TASK_QUEUE. From block  2208 , control passes to block  2209 . 
     In block  2209 , the runtime determines if post-treatment of producers has to be skipped. If benchmarking is enabled, producers may be executed locally as well as multiprocessed. Thus, post-treatment of the producers is skipped after local execution. More details of benchmarking are discussed below. Referring back to  FIG. 22A , if post-treatment has to be skipped, then control passes to block  2248  in  FIG. 22B . Otherwise, control passes to block  2210 . 
     In block  2210 , the producers of the current set of ready producers are sorted by type—standard producers go to block  2220  and dependency determination producers go to block  2235 . In one embodiment of the invention, block  2210  is performed by checking the return class of the producer. With reference to the  FIGS. 10 and 11D , the method tracking structure is accessed to determine if the output class of the producer is DEP, and thus this producer is a dependency determination producer. 
     In block  2220 , for those parents, if any, that have an absorbing subscription on any of these executed standard producers, the subscription is marked as incomplete. With reference to  FIG. 14A , the appropriate row of the completed column  1420  is set to indicate incomplete. 
     In block  2235 , a new producer command is executed for any discovered producers, and subscription logging and processing is performed for any subscriptions, then control passes to block  2240 . The new producer command part of block  2235  is performed in similar manner to block  1750 , while the subscription logging and processing is performed in similar manner to blocks  1740  and  1745 . 
     In block  2240 , add to the set of candidate producers newly added to the execution start log. From block  2240 , control passes to block  2245 . Block  2240  is performed in similar manner to block  2200 , except only producers newly added to the execution start log as a result of block  2235  are added to the set of candidate producers. 
     In block  2245 , the producers that were executed are marked as executed, the producer output caching (and instance caching) are updated as necessary, the producer metrics (if acquired) are updated in the producer graph structure  1060  in  FIG. 10 , any parent producers of the producers that were executed are added to the current set of candidate producers, and the producers that were executed are removed from the current set of candidate and ready producers. In some embodiments, the producer metrics may be updated by reading the corresponding task metrics and the corresponding job reference. Using the job reference, the job metrics may be read from a job metrics map. Alternatively, the producer metrics may be updated by reading the task metrics and the job metrics if a job metrics map is not used. More details of the task metrics, the job metrics, and the job metrics map are discussed below. From block  2245 , control passes to block  2248 . 
     In block  2248 , the result task queues are checked to determine if all of them are empty. If at least one of the result task queues is not empty, then control passes back to block  2208  to continue process the result in the non-empty result task queue(s). Otherwise, if all of the result task queues are empty, then control passes to block  2250 . 
     In block  2250 , it is determined if the set of ready producers is empty. If not, control passes back to block  2205 ; otherwise, control passes to block  2255 . 
     In block  2255 , it is determined in all subscriptions have been completed. If so, control passes to block  2265  where the flow diagram ends; otherwise, control passes to block  2260 . With reference to the embodiment of the invention in  FIG. 14A , the subscription type column  1405  and the complete column  1420  are scanned for any absorbing subscriptions that are not completed. 
     In block  2260 , the incomplete absorbing subscriptions are processed and control passes back to block  2205 . An exemplary manner of performing block  2260  is described later herein. 
       FIG. 23  is a flow diagram for block  2205  of  FIG. 22  according to one embodiment of the invention. Thus, control flows from block  2200  to block  2305  in block  2205 . In block  2305 , for each producer in the set of candidate producers, the following blocks  2310 - 2325  are performed. 
     In block  2310 , it is determined if the producer has any absorbing subscription dependency that is incomplete. If so, control passes to block  2325 ; otherwise, control passes to block  2315 . With reference to the embodiment of  FIG. 14A , the subscriber&#39;s producer key column  1400  and subscription type column  1405  is scanned for a matching to the current selected producer and absorbing subscription type; and if a match is found, the completed column  1420  at the appropriate row is checked to determine the status of that absorbing subscription dependency. 
     In block  2315 , it is determined if the producers on which the currently selected producer depends are executed. If not, control passes to block  2315 ; otherwise, control passes to block  2320 . With regard to the embodiment of the invention shown in  FIG. 11C , the incremental execution markings column  1180  for the rows of the child dependencies are checked to determined the execution status of the currently selected producer&#39;s children. 
     In block  2320 , the currently selected candidate producer is added to the current set of ready producers and control passes to block  2325 . 
     In block  2325 , the flow ends for the current produced selected in block  2305 . 
       FIG. 24  is a flow diagram for block  2260  of  FIG. 22B  according to one embodiment of the invention. Thus, control flows from block  2255  to block  2505  in block  2260 . In block  2505 , for each producer with an absorbing subscription dependency that is incomplete, the following blocks  2510 - 2525  are performed. 
     In block  2510 , it is determined if all matching producers have been executed. If so, control passes to block  2515 ; otherwise, control passes to block  2525 . With reference to the embodiments of  FIGS. 11C and 14A , the matching producers column  1415  at the appropriate row is access to determine the matching producers, and the incremental execution column  1180  at the appropriate rows is checked for each of the matching producers. 
     In block  2515 , the absorbing subscription is marked as complete and control passes to block  2520 . With reference to the embodiments of  FIG. 14A , the complete column  1420  at the appropriate row is set to indicate complete. 
     In block  2520 , the producer selected in block  2505  is added to the current set of candidate producers and control passes to block  2525 . 
     In block  2525 , the flow ends for the producer selected in block  2505 . 
       FIGS. 25 and 26  are flow diagrams for block  2207  of  FIG. 22  according to one embodiment of the invention. Thus, control flows from block  2205  to block  2610  in  FIG. 25 . In block  2610 , instantiation of various task queues for multiprocessing, multithreading, and local execution and a job for multiprocessing is performed. An exemplary manner of performing block  2610  is described later herein. From block  2610 , control passes to block  2620 . 
     In block  2620 , the set of ready producers are scanned to process the producers in the set one by one. From block  2620 , control passes to block  2622 . 
     In block  2622 , an execution mode of a producer is read from a producer graph structure, such as the graph structure in  FIG. 11C . Then control passes to block  2625 . 
     In block  2625 , a task referencing the producer and the output of the producer is created. From block  2625 , control passes to block  2630 . 
     In block  2630 , it is determined which execution mode the producer should be executed in. In some embodiments, there are three execution modes supported, namely, multiprocessing, multithreading, and local execution. If the execution mode is determined to be local execution, control passes to block  2632 . If the execution mode is determined to be multithreading, control passes to block  2634 . If the execution mode is determined to be multiprocessing, control passes to block  2635 . 
     In block  2632 , the task of the producer is pushed into the execution task queue for local execution, i.e., LOCAL_EXECUTION_TASK_QUEUE. Then control passes to block  2640 . 
     In block  2634 , the task of the producer is pushed into the execution task queue for multithreading, i.e., MT_EXECUTION_TASK_QUEUE. Then control passes to block  2640 . 
     In block  2635 , the task of the producer is pushed into the execution task queue for multiprocessing, i.e., MP_EXECUTION_TASK_QUEUE. Then control passes to block  2636 . In block  2636 , it is determined whether benchmarking between distant execution and local execution is requested. If not, control passes to block  2640 . However, if benchmarking is requested, control passes to block  2637 . 
     In block  2637 , the task pushed into MP_EXECUTION_TASK_QUEUE is marked to skip post-execution treatment. Then a new task referencing the producer and the output of the producer is created and is pushed into the execution task queue for local execution, i.e., LOCAL_EXECUTION_TASK_QUEUE, as well in block  2638 . Then control passes to block  2639  to store in the task added to the MP_EXECUTION_TASK_QUEUE a reference to the task added to the LOCAL_EXECUTION_TASK_QUEUE for later matching. After block  2639 , control passes to block  2640 . 
     In block  2640 , it is determined if all producers in the set of ready producers have been scanned. If not, control passes back to block  2620  to continue scanning producers in the set of ready producers. Otherwise, control passes to block  2642  in  FIG. 26B . 
     In block  2642 , the runtime determines if the MT_EXECUTION_TASK_QUEUE is empty. If so, control passes to  2660 . Otherwise, control passes to block  2644 . 
     In block  2644 , the runtime initiates a thread pooling mechanism if not already initiated. From block  2644 , control passes to block  2650 . 
     In block  2650 , a separate thread is instantiated to perform multithreading on the tasks in MT_EXECUTION_TASK_QUEUE. An exemplary manner of performing block  2650  is described later herein. From block  2650 , control passes to block  2660 . 
     In block  2660 , multiprocessing and local execution are performed to execute the tasks in MP_EXECUTION_TASK_QUEUE_and LOCAL_EXECUTION_TASK_QUEUE. An exemplary manner of performing block  2660  is described later herein. From block  2660 , control passes to block  2670 . 
     In block  2670 , it is determined if the current size of MT_RESULT_TASK_QUEUE is equal to the initial size of MT_EXECUTION_TASK_QUEUE. If not, then control remains in block  2670  because multithreading has not been completed yet on all tasks in MT_EXECUTION_TASK_QUEUE. Otherwise, control passes from block  2670  to block  2690  and the process in block  2207  ends. Although multithreading, multiprocessing, and local execution are performed sequentially in the exemplary flow described above, it should be appreciated that any combination of multithreading, multiprocessing, and local execution may be performed in parallel in some alternative embodiments. 
       FIGS. 27A and 27B  are flow diagrams for block  2610  of  FIG. 26  according to one embodiment of the invention. Thus, control flows from block  2205  to block  2710  in  FIG. 27A . In block  2710 , it is determined if MT_RESULT_TASK_QUEUE is instantiated. If yes, then MT_RESULT_TASK_QUEUE is cleared in block  2715 . Otherwise, MT_RESULT_TASK_QUEUE is instantiated in block  2713 . Then control passes from block  2713  or block  2715  to block  2720 . 
     In block  2720 , it is determined if MT_EXECUTION_TASK_QUEUE is instantiated. If yes, then MT_EXECUTION_TASK_QUEUE is cleared in block  2725 . Otherwise, MT_EXECUTION_TASK_QUEUE is instantiated in block  2723 . Then control passes from block  2723  or block  2725  to block  2730 . 
     In block  2730 , it is determined if MP_RESULT_TASK_QUEUE is instantiated. If yes, then MP_RESULT_TASK_QUEUE is cleared in block  2735 . Otherwise, MP_RESULT_TASK_QUEUE is instantiated in block  2733 . Then control passes from block  2733  or block  2735  to block  2740 . 
     In block  2740 , it is determined if MP_EXECUTION_TASK_QUEUE is instantiated. If yes, then MP_EXECUTION_TASK_QUEUE is cleared in block  2745 . Otherwise, MP_EXECUTION_TASK_QUEUE is instantiated in block  2743 . Then control passes from block  2743  or block  2745  to block  2750  in  FIG. 27B . 
     In block  2750 , it is determined if LOCAL_RESULT_TASK_QUEUE is instantiated. If yes, then LOCAL_RESULT_TASK_QUEUE is cleared in block  2755 . Otherwise, LOCAL_RESULT_TASK_QUEUE is instantiated in block  2753 . Then control passes from block  2753  or block  2755  to block  2760 . 
     In block  2760 , it is determined if LOCAL_EXECUTION_TASK_QUEUE is instantiated. If yes, then LOCAL_EXECUTION_TASK_QUEUE is cleared in block  2765 . Otherwise, LOCAL_EXECUTION_TASK_QUEUE is instantiated in block  2763 . Then control passes from block  2763  or block  2765  to block  2620 . 
       FIG. 28A  is a flow diagram for a process to perform multithreading according to one embodiment of the invention. As discussed above, a separate thread is instantiated in block  2650  of  FIG. 26  to perform multithreading. 
     In block  2820 , it is determined if MT_EXECUTION_TASK_QUEUE is empty. If the MT_EXECUTION_TASK_QUEUE is empty, that is all task in MT_EXECUTION_TASK_QUEUE have been fed to a corresponding execution thread, then the process ends. Otherwise, that is, there is at least one task to be fed to an execution thread, then control passes to block  2825  to determine if there is any thread available in the pool. If there is no thread available in the pool, control remains in block  2825  until there is an available thread. When there is an available thread, control passes to block  2830 . 
     In block  2830 , a task is removed from MT_EXECUTION_TASK_QUEUE and the removed task is fed to the available thread. Then control passes back to block  2820  to repeat blocks  2820 ,  2825 , and  2830  until all tasks have been removed from MT_EXECUTION_TASK_QUEUE. Note that the process in blocks  2820 ,  2825 , and  2830  may be performed by an instantiated thread in order to avoid blocking the rest of the flow. 
       FIG. 28B  is a flow diagram illustrating the execution of a task within a thread along with optional metrics acquisition. If instrumentation is requested, then the runtime starts measuring task execution time in block  2810 . Otherwise, block  2810  is skipped. From block  2810 , control passes to block  2831 . In block  2831 , a task within a thread is executed by calling the method of the task with the appropriate instance and inputs. When execution of the task is done, outputs and/or the modified instance are returned from the method and the thread is terminated. From block  2831 , control passes to block  2815 . If instrumentation is requested, then the runtime ends measuring task execution time in block  2815 . Otherwise, block  2815  is skipped. 
       FIG. 28C  is a flow diagram for a process responsive to thread termination callback according to one embodiment of the invention. In block  2832 , a thread termination callback is received. 
     In block  2834 , the output of the task within the terminated thread and the metrics acquired (such as the task execution time), if any, is stored in the task executed by the terminated thread and the task with the output and the metrics acquired, if any, is pushed into MT_RESULT_TASK_QUEUE. Then control passes to block  2836 . In block  2836 , the terminated thread is marked as available in the pool of threads. 
       FIGS. 29A and 29B  are flow diagrams for block  2660  of  FIG. 26  according to one embodiment of the invention. Thus, control flows from block  2650  to block  2910  in  FIG. 29A . Note that blocks that are performed for instrumentation, but are not used to implement parallelization of producer execution, are illustrated with blocks having broken dashed boundaries in  FIGS. 29A and 29B . 
     In block  2910 , it is checked if MP_EXECUTION_TASK_QUEUE is empty. If MP_EXECUTION_TASK_QUEUE is empty, there is no task to be multiprocessed and thus, control passes to block  2670 . Otherwise, control passes to block  2915 . 
     In block  2915 , a job is instantiated and a job identifier (ID) is allocated to the job. Furthermore, a TASKS_LOCAL_MAP is instantiated in block  2915  as well. Then control passes to block  2918 . If instrumentation is requested, block  2918  is performed to start measuring job overall time. Otherwise, block  2918  is skipped. Then control passes to block  2920 . 
     In block  2920 , a task is read and removed from MP_EXECUTION_TASK_QUEUE. Control then passes to block  2921 . If instrumentation is requested, block  2921  is performed to start measuring task overall time. Otherwise, block  2921  is skipped. Then control passes to block  2923 . 
     In block  2923 , a unique task identifier (ID) is allocated to the task and stored with the task reference in TASKS_LOCAL_MAP. Then control passes to block  2925  to instantiate a task serialized form and fill the task serialized form with the task ID, a class name, and a method name of the producer corresponding to the task. Then control passes to block  2930 . 
     In block  2930 , a serialized form of each one of all input producers and the underlying instance is found if already created. Alternatively, if a serialized form is not yet created, it is created in block  2930 . Exemplary manner to perform block  2930  is discussed herein. From block  2930 , control passes to block  2960 . 
     In block  2960 , the task serialized form is added to a serialized task execution queue of the job, namely, JOB.SERIALIZED_TASKS_EXECUTION_QUEUE. Then control passes to block  2965 . 
     In block  2965 , it is determined if MP_EXECUTION_TASK_QUEUE is empty. If MP_EXECUTION_TASK_QUEUE is not empty, control passes back to block  2920  to continue going through the remaining tasks in MP_EXECUTION_TASK_QUEUE. Otherwise, control passes to block  2970 . 
     In block  2970 , the job is sent to a grid of a number of distant processors. The grid of processors performs distant computing to execute the job. Details of one exemplary flow of distant computing are discussed herein. Then control passes to block  2972  to perform local execution. From block  2972 , control passes to block  2973 . 
     In block  2973 , it is determined if the job is done. If not, control remains in block  2973  until the job is done. When the job is done, control passes to block  2975  in  FIG. 29B . 
     Referring to  FIG. 29B , a job virtual local processing time is set to zero in block  2975 . According to one aspect of the invention, the job virtual local processing time is the time would have taken all the tasks of the job to be executed locally. From block  2975 , control is passed to block  2977 . 
     In block  2977 , a task is read and removed from the serialized result queue of the job, i.e., JOB.SERIALIZED_TASKS_RESULTS_QUEUE. Then control is passed to block  2979  to find the task reference using the task ID stored in the TASKS_LOCAL_MAP. Then control passes to block  2980 . 
     If instrumentation is requested, block  2980  is performed to determine the output serialized form size and to start measuring local deserialization time of the output. Otherwise, block  2980  is skipped and control passes to block  2981 . In block  2981 , the output in the task output is deserialized. From block  2981 , control passes to block  2982 . Again, if instrumentation is requested, block  2982  is performed to end measuring local deserialization time. Further, if instrumentation is requested, blocks  2984 ,  2985 ,  2987 , and  2989  may be performed. Otherwise, blocks  2984 ,  2985 ,  2987 , and  2989  are skipped and control passes from block  2981  to block  2990 . 
     In block  2984 , the runtime ends measuring task overall time and then removes local execution time from the task overall time. From block  2984 , control passes to block  2985 . 
     In block  2985 , it is determined whether benchmarking is requested. If benchmarking is requested, control passes to block  2987  and then to block  2989 . Otherwise, control passes to  2989  from  2985  to skip block  2987 . 
     As discussed above with reference to  FIGS. 25 and 26 , benchmarking is requested to compare local and distant execution times. Thus, a task is executed both locally and distantly using multiprocessing if benchmarking is requested according to one embodiment of the invention. Thus, if benchmarking is requested, the runtime may find a corresponding task in LOCAL_RESULT_TASK_QUEUE in block  2987 . Further, the runtime may add the local processing time stored in the task to the job virtual local processing time. As such, the job virtual local processing time equals to the sum of the local processing times of all tasks in the job when all tasks have been executed. From block  2987 , control passes to block  2989 . 
     In block  2989 , the task metrics, such as task overall time, along with the job ID are added to the task. Then control passes to block  2990 . Note that both blocks  2987  and  2989  are performed if instrumentation is requested. Otherwise, both blocks  2987  and  2989  may be skipped. 
     In block  2990 , the task is pushed in MP_RESULT_TASK_QUEUE. Then control passes to block  2991 . In block  2991 , it is determined if JOB.SERIALIZED_TASKS_RESULTS_QUEUE is empty. If not, then control passes back to block  2977  to continue reading tasks from the queue and deserializing the outputs. Otherwise, control passes to block  2992  if instrumentation is requested. If instrumentation is not requested, then control passes from block  2991  to block  2670  in  FIG. 26B . 
     If instrumentation is requested, blocks  2992 ,  2993 ,  2995 ,  2996 , and  2997  may be performed. Otherwise, blocks  2992 ,  2993 ,  2995 ,  2996 , and  2997  may be skipped. In block  2992 , the measuring of job overall time is ended and then local execution time is removed from the job overall time. From block  2992 , control passes to block  2993 . 
     In block  2993 , it is determined if benchmarking is requested. If benchmarking is requested, control passes to block  2995 . In block  2995 , the job speedup is computed by dividing the job virtual local processing time with the job overall time. Then control passes from block  2995  to block  2996 . In block  2996 , job efficiency is computed by dividing the job speedup with the number of processors available and dedicated to the execution of the job in the grid. From block  2996 , control passes to block  2997 . Otherwise, if benchmarking is not requested, control passes from block  2993  to block  2997  directly. 
     In block  2997 , the metrics of the job (e.g., job speedup, job efficiency, job overall time, etc.) are added to each task within the job. From block  2997 , control passes to block  2670  in  FIG. 26B . 
       FIG. 30  shows a flow diagram for block  2930  of  FIG. 29A  according to one embodiment of the invention. Thus, control flows from block  2925  to block  3010  in  FIG. 30 . In block  3010 , it is determined if a serialized form of an input producer or of the underlying instance is already created in the SERIALIZED_FORM_LOCAL_MAP based on the input producer key or the underlying instance key. If the serialized form is already created, control passes to block  3015 . Otherwise, control passes to block  3020 . 
     In block  3015 , the serialized form ID and the serialized form are read from the SERIALIZED_FORM_LOCAL_MAP. Then control passes to block  3040 . 
     In block  3020 , a serialized form identifier is allocated to the input producer or the underlying instance. Then control passes to block  3022 . 
     In block  3022 , the measurement of local serialization time is started. Then control passes to block  3024 . 
     In block  3024 , a serialized form is created for the input producer or the underlying instance. Then control passes to block  3026 . 
     In block  3026 , the measurement of local serialization time is ended. Then control passes to block  3028 . 
     In block  3028 , the input serialized form size is determined. Then control passes to block  3030 . 
     In block  3030 , the input producer key or the underlying instance key, the serialized form ID, and the serialized form are stored in the SERIALIZED_FORM_LOCAL_MAP. The SERIALIZED_FORM_LOCAL_MAP may be global or allocated and freed on a job by job basis, depending on various factors, such as memory requirements, performance requirements, etc. Then control passes to block  3034 . 
     In block  3034 , the input serialized form size and the serialization time are stored with the serialized form ID in the SERIALIZED_FORM_LOCAL_MAP. Then control passes to block  3040 . Note that blocks  3022 ,  3026 ,  3028 , and  3034  described above are performed if instrumentation is requested. Blocks  3022 ,  3026 ,  3028 , and  3034  may be skipped if instrumentation is not requested. 
     In block  3040 , it is determined if the serialized form ID is in the JOB.SERIALIZED_FORM_MAP. If yes, then control passes to block  3045 . Otherwise, control passes to block  3043 . 
     In block  3043 , the serialized form ID and the serialized form are stored in JOB.SERIALIZED_FORMS_MAP. Then control passes to block  3045 . 
     In block  3045 , the serialized form ID is added as an input or as an underlying instance to the task serialized form. From block  3045 , control passes to block  3050 . 
     In block  3050 , it is determined if there is any more input producer not yet processed or if the underlying instance is not yet processed. If there is, then control passes back to block  3010 . Otherwise, control passes to block  2960  in  FIG. 29A . 
       FIGS. 31A and 31B  show flow diagrams of distant computing for multiprocessing according to one embodiment of the invention. Again, blocks illustrated with broken dash line are performed if instrumentation is requested and may be skipped if instrumentation is not requested. As discussed above, a job including a number of tasks corresponding to producers is dispatched to a grid of processors for execution. Each processor in the grid, also referred to as a worker, may cache the JOB_SERIALIZED FORMS_MAP. For example, if a job holds a thousand tasks and there are ten workers executing these tasks, the JOB_SERIALIZED FORMS_MAP is sent once by the grid dispatcher to each worker, and cached at worker level. When the job is finished, the grid dispatcher sends a command to the worker in order to free up the cache. The flow starts at block  3108 . 
     In block  3108 , the JOB_SERIALIZED_FORMS_MAP along with the task serialized form holding input IDs, class name, and method name are received from the grid dispatcher. Then control passes to block  3110 . In block  3110 , a class is located using the class name and a method is located using the method name. The class and the method are loaded to reconstitute a task. Then control passes to block  3112 . 
     In block  3112 , a task input ID or the instance ID is looked up from the JOB.SERIALIZED_FORMS_MAP. Then control passes to block  3120 . 
     In block  3120 , it is determined if the input ID is found. If not, control passes to block  3190  to return an error. Otherwise, control passes to block  3130 . 
     In block  3130 , it is determined if the JOB.SERIALIZED_FORMS_MAP entry corresponding to the input ID is already deserialized. If it is already deserialized, then control passes to block  3150 . Otherwise, control passes to block  3132 . 
     In block  3150 , the deserialized form of the input is extracted. Then control passes to block  3155 . 
     In block  3132 , the measurement of distant deserialization time is started. Then control passes to block  3134  to deserialize the JOB.SERIALIZED_FORMS_MAP entry corresponding to the input ID. From block  3134 , control passes to block  3136 . In block  3136 , the measurement of distant deserialization time is ended. Then control passes to block  3138 . 
     In block  3138 , the corresponding entry in the JOB.SERIALIZED_FORMS_MAP is enriched with the deserialized form. Then control passes to block  3143 . 
     In block  3143 , the instance or the standard input is added to the task definition. Then control passes to block  3155 . 
     In block  3155 , it is determined if all input IDs (i.e., all standard inputs along with the underlying instance) have been processed. In other words, it is determined if the task has been completely reconstituted or deserialized. If so, control passes to block  3160  in  FIG. 31B . Otherwise, control passes back to block  3112  to process the next input ID. 
     Referring to  FIG. 31B , the measurement of distant processing time is started in block  3160 . Then control passes to block  3162 . 
     In block  3162 , the method with the appropriate instance and inputs is called. As a consequence of the execution, the method may return an output and/or modify the instance of the method. The runtime receives the output returned from the method and/or the modified instance. Then control passes from block  3162  to block  3166 . 
     In block  3166 , the measurement of distant processing time is ended. Then control passes to block  3170 . 
     In block  3170 , the measurement of distant serialization time is started. Then control passes to block  3172  to serialize the returned output and/or the modified instance and attach the serialized output and/or the serialized modified instance to the task. Then control passes to block  3174 . In block  3174 , the measurement of distant serialization time is ended. From block  3174 , control passes to block  3176 . 
     In block  3176 , the metrics (e.g., distant serialization time, distant deserialization time, etc.) are stored in the task. Then control passes to block  3180 . 
     In block  3180 , the task is sent back to the grid dispatcher of the runtime and the flow ends. Again, blocks illustrated with broken dash line are performed if instrumentation is requested and may be skipped if instrumentation is not requested. 
       FIG. 32  shows a flow diagram for block  2972  of  FIG. 29A  according to one embodiment of the invention. Thus, control flows from block  2970  to block  3202  in  FIG. 32 . Again, blocks illustrated with broken dash line are performed if instrumentation is requested and may be skipped if instrumentation is not requested. 
     In block  3202 , the measurement of local execution time is started. Then control passes to block  3210 . 
     In block  3210 , a task is removed from LOCAL_EXECUTION_TASK_QUEUE and is executed locally by calling the method with the appropriate instance and inputs. When execution is done, the method returns outputs and/or the modified instance of the method. Then control passes to block  3212 . 
     In block  3212 , the measurement of local execution time is ended. Then control passes to block  3220 . 
     In block  3220 , the output of the task is stored in the task. Then control passes to block  3223 . 
     In block  3223 , the metrics (e.g., local execution time) is stored in the task as well. Then control passes to block  3230 . 
     In block  3230 , the task is pushed into the LOCAL_RESULT_TASK_QUEUE. From block  3230 , control passes to block  3240 . 
     In block  3240 , it is determined if the LOCAL_EXECUTION_TASK_QUEUE is empty. If the queue is empty, then control passes to block  2973  in  FIG. 29A . Otherwise, control passes back to block  3202  to repeat the process to execute another task locally. 
     Alternative Embodiments 
     While the flow diagrams in the figures show a particular order of operations performed by certain embodiments of the invention, it should be understood that such order is exemplary (e.g., alternative embodiments may perform the operations in a different order, combine certain operations, overlap certain operations, etc.) 
     While the invention has been described in terms of several embodiments, those skilled in the art will recognize that the invention is not limited to the embodiments described, can be practiced with modification and alteration within the spirit and scope of the appended claims. The description is thus to be regarded as illustrative instead of limiting.