Patent Publication Number: US-7584207-B2

Title: Customization of metadata describing objects in a computing environment

Description:
The present application is a continuation of and claims priority of U.S. patent application Ser. No. 10/387,508, filed Mar. 12, 2003, the content of which is hereby incorporated by reference in its entirety. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to a computing environment in which source code is used to implement applications and programs desired by a user. More specifically, the present invention relates to a framework which enables customization of the computer programs or applications without modifying the source code. 
   One approach to designing and marketing computer software-related products is to focus on horizontal functionality such that the product is broadly applicable across large industry segments, and across many different countries. Such a system may also desirably promote an aftermarket to meet the unique needs of specific vertical target markets and specific companies. Similarly, the product may desirably promote a customer&#39;s ability to change or customize the product to their individual needs. 
   If the product cannot be extended to meet the unique needs of a customer, it essentially requires a customer to change its business to match the software which the customer has just purchased. Of course, these types of systems are resisted by customers, since changes to business activities can be costly and time consuming. 
   There are a number of different techniques which have been conventionally used in order to enable a system to be customized. Such conventional techniques include, for example, source code modification. This technique entails providing customers with copies of the source code for the product. It thus allows a well trained practitioner to change significant amounts of content, and those changes can be made to look as if they are part of the product, because in effect, they are part of the modified source code product. 
   However, source code modification carries with it significant drawbacks. For example, source code modification costs a significant amount of money prior to using the product, because the user or customer must often hire expensive consultants and developers who have been specifically trained in the nuances of how the product is built. The user must then endure the risk of estimating a problem, which is a very difficult and imprecise task. Even if these problems can be overcome and persevered, the result is modified source code. When the manufacturer of the original source code ships additional software, such as bug fixes, updates, and new versions, the customer is either forced to again hire talented engineers or developers (and hopefully the same ones who made the original modifications), in order to merge those modifications into the new source code shipped by the manufacturer, and to resolve issues, one-by-one, as they arise in the newly modified source code. Alternatively, the user can simply go without the bug fixes and new features that may benefit the user&#39;s business. 
   In addition, source code modification makes it extremely difficult to simply purchase add-on modules “off the shelf” from multiple different vendors, because each of those vendors will likely have to modify the source code as well to accommodate their specific off the shelf modules. Consequently, not only must the manufacturer ship the source code of the base product, but each add-on vendor must ship their source as well. The user must then conduct some sort of adhoc merge process or synthesize a single product out of these random sets of source code. Of course, this results in a brittle set of code that is virtually guaranteed to have problems with upgrades or when any one of the vendors ships a bug fix. 
   Source code modification also suffers from the problem that only one organization in the world (the specific developers or engineers who modified the source code) knows how the modified source code product was built. Therefore, it is difficult, if not impossible, to achieve economies of scale and product support for any of the products running at the customer site. 
   The problems with source code modification increase significantly when, even within a single customer, there exists a diverse set of users with a diverse set of needs and preferences. Every time one of those users changes the product through the source code modification strategy in order to accommodate their particular needs, the customer employing those users, in effect, ends up with a new source code base. In other words, the customer does not only have a single custom code base, but it may actually have many custom code bases, depending upon how many specific users or departments within the customer have modified the code base. Again, each time a bug fix is published or a change is made to a customization that applies to all users, the customer must go through some sort of merge process with all other copies of the source which have been made. 
   This is only a partial list of the many problems associated with source code modification techniques. These problems can result in a great deal of difficulty for the management of the customer, and the employees themselves. 
   Another technique which enables some limited modification of a computer program that is based on objects includes the addition of user fields which can be defined by the user. In other words, each object which is to be “customizable” is initially defined to have one or more user fields which can be defined or used by the user, as the user wishes. While this does allow some type of customization, it does not solve all the problems mentioned above. It also carries with it a large number of its own problems. For example, the naming convention associated with the user fields makes it non-intuitive and difficult to associate the specific uses of those user fields. For instances, the additional user fields are typically named with very general names such as “USERFIELD. 1 ” to “USERFIELD.N” It is difficult, if not impossible, for the users to remember what each user field has been used for. In addition, the additional user fields do not solve problems associated with multi-vendors or multiple modifications by different organizations. For example, if one vendor or one user assigns the user fields in a first way, but another vendor or user assigns the same user fields in a different way, then there is inconsistency in how the user fields are defined, and the two products associated with the two vendors or users will not work together without even further modification. 
   Other techniques for customizing have been tried as well. For example, customizations can be made by writing custom event code. Then, by using a one-to-one mapping to the original objection in the source code, the “customized” object can be manipulated when an event occurs on the original object. Another technique previously used is to include “property bags” or name-value pairs. Both of these techniques also have significant drawbacks and do not remedy the deficiencies associated with source code modification. 
   SUMMARY OF THE INVENTION 
   The present invention facilitates customization of metadata that describes objects in a software system without requiring modification of source code. A customization that describes a desired customization to metadata is received and the relevant metadata is identified. A delta value indicating the customization to the metadata is stored. 
   In one embodiment, when subsequently accessing the customized metadata, the delta value is retrieved. The metadata to be customized is replaced with the delta value. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram of one environment in which the present invention can be used. 
       FIG. 2  is a block diagram of an object-relational (or entity-relational) database system. 
       FIG. 3  is a UML class diagram of a customization framework in accordance with one embodiment of the present invention. 
       FIG. 4  is a block diagram illustrating one embodiment of maintaining context in accordance with the present invention. 
       FIG. 5  illustrates an entity extension system in accordance with one embodiment of the present invention. 
       FIG. 6A  illustrates the entity extension system shown in  FIG. 5 , after entities have been customized, or extended, in accordance with one embodiment of the present invention. 
       FIG. 6B  is a flow diagram illustrating how entities are extended in accordance with one embodiment of the present invention. 
       FIG. 6C  is a block diagram illustrating how entities are customized by changing relations among entities in accordance with one embodiment of the present invention. 
       FIG. 7A  illustrates one embodiment of a metadata structure and customizations in accordance with one embodiment of the present invention. 
       FIG. 7B  illustrates one embodiment of a conflict resolution table. 
       FIGS. 8A-8C  are screen shots illustrating one example of a customization of a system screen in accordance with one embodiment of the present invention. 
       FIG. 9  is a block diagram of one embodiment of a representation of a business activity. 
       FIG. 10  illustrates one embodiment of customization of a business activity through metadata customization. 
   

   DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
   The present invention relates to customization of computer software. However, prior to discussing the present invention in greater detail, one embodiment of an illustrative environment in which the present invention can be used will be discussed. 
     FIG. 1  illustrates an example of a suitable computing system environment  100  on which the invention may be implemented. The computing system environment  100  is only one example of a suitable computing environment and is not intended to suggest any limitation as to the scope of use or functionality of the invention. Neither should the computing environment  100  be interpreted as having any dependency or requirement relating to any one or combination of components illustrated in the exemplary operating environment  100 . 
   The invention is operational with numerous other general purpose or special purpose computing system environments or configurations. Examples of well known computing systems, environments, and/or configurations that may be suitable for use with the invention includes but are not limited to, personal computers, server computers, hand-held or laptop devices, multiprocessor systems, microprocessor-based systems, set top boxes, programmable consumer electronics, network PCs, minicomputers, mainframe computers, distributed computing environments that include any of the above systems or devices, and the like. 
   The invention may be described in the general context of computer-executable instructions, such as program modules, being executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. The invention may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote computer storage media including memory storage devices. 
   With reference to  FIG. 1 , an exemplary system for implementing the invention includes a general purpose computing device in the form of a computer  110 . Components of computer  110  may include, but are not limited to, a processing unit  120 , a system memory  130 , and a system bus  121  that couples various system components including the system memory to the processing unit  120 . The system bus  121  may be any of several types of bus structures including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures. By way of example, and not limitation, such architectures include Industry Standard Architecture (ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, Video Electronics Standards Association (VESA) local bus, and Peripheral Component Interconnect (PCI) bus also known as Mezzanine bus. 
   Computer  110  typically includes a variety of computer readable media. Computer readable media can be any available media that can be accessed by computer  110  and includes both volatile and nonvolatile media, removable and non-removable media. By way of example, and not limitation, computer readable media may comprise computer storage media and communication media. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by computer  110 . Communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. The term “modulated data signal” means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared and other wireless media. Combinations of any of the above should also be included within the scope of computer readable media. 
   The system memory  130  includes computer storage media in the form of volatile and/or nonvolatile memory such as read only memory (ROM)  131  and random access memory (RAM)  132 . A basic input/output system  133  (BIOS), containing the basic routines that help to transfer information between elements within computer  110 , such as during start-up, is typically stored in ROM  131 . RAM  132  typically contains data and/or program modules that are immediately accessible to and/or presently being operated on by processing unit  120 . By way of example, and not limitation,  FIG. 1  illustrates operating system  134 , application programs  135 , other program modules  136 , and program data  137 . 
   The computer  110  may also include other removable/non-removable volatile/nonvolatile computer storage media. By way of example only,  FIG. 1  illustrates a hard disk drive  141  that reads from or writes to non-removable, nonvolatile magnetic media, a magnetic disk drive  151  that reads from or writes to a removable, nonvolatile magnetic disk  152 , and an optical disk drive  155  that reads from or writes to a removable, nonvolatile optical disk  156  such as a CD ROM or other optical media. Other removable/non-removable, volatile/nonvolatile computer storage media that can be used in the exemplary operating environment include, but are not limited to, magnetic tape cassettes, flash memory cards, digital versatile disks, digital video tape, solid state RAM, solid state ROM, and the like. The hard disk drive  141  is typically connected to the system bus  121  through a non-removable memory interface such as interface  140 , and magnetic disk drive  151  and optical disk drive  155  are typically connected to the system bus  121  by a removable memory interface, such as interface  150 . 
   The drives and their associated computer storage media discussed above and illustrated in  FIG. 1 , provide storage of computer readable instructions, data structures, program modules and other data for the computer  110 . In  FIG. 1 , for example, hard disk drive  141  is illustrated as storing operating system  144 , application programs  145 , other program modules  146 , and program data  147 . Note that these components can either be the same as or different from operating system  134 , application programs  135 , other program modules  136 , and program data  137 . Operating system  144 , application programs  145 , other program modules  146 , and program data  147  are given different numbers here to illustrate that, at a minimum, they are different copies. 
   A user may enter commands and information into the computer  110  through input devices such as a keyboard  162 , a microphone  163 , and a pointing device  161 , such as a mouse, trackball or touch pad. Other input devices (not shown) may include a joystick, game pad, satellite dish, scanner, or the like. These and other input devices are often connected to the processing unit  120  through a user input interface  160  that is coupled to the system bus, but may be connected by other interface and bus structures, such as a parallel port, game port or a universal serial bus (USB). A monitor  191  or other type of display device is also connected to the system bus  121  via an interface, such as a video interface  190 . In addition to the monitor, computers may also include other peripheral output devices such as speakers  197  and printer  196 , which may be connected through an output peripheral interface  195 . 
   The computer  110  may operate in a networked environment using logical connections to one or more remote computers, such as a remote computer  180 . The remote computer  180  may be a personal computer, a hand-held device, a server, a router, a network PC, a peer device or other common network node, and typically includes many or all of the elements described above relative to the computer  110 . The logical connections depicted in  FIG. 1  include a local area network (LAN)  171  and a wide area network (WAN)  173 , but may also include other networks. Such networking environments are commonplace in offices, enterprise-wide computer networks, intranets and the Internet. 
   When used in a LAN networking environment, the computer  110  is connected to the LAN  171  through a network interface or adapter  170 . When used in a WAN networking environment, the computer  110  typically includes a modem  172  or other means for establishing communications over the WAN  173 , such as the Internet. The modem  172 , which may be internal or external, may be connected to the system bus  121  via the user-input interface  160 , or other appropriate mechanism. In a networked environment, program modules depicted relative to the computer  110 , or portions thereof, may be stored in the remote memory storage device. By way of example, and not limitation,  FIG. 1  illustrates remote application programs  185  as residing on remote computer  180 . It will be appreciated that the network connections shown are exemplary and other means of establishing a communications link between the computers may be used. 
     FIG. 2  is a block diagram of an object-relational (or entity-relational) data storage system. In the present discussion, entities will be referred to in a manner that is interchangeable with the term “objects”. E-R system  200  includes a set of entities (or objects)  202  which correspond to data stored in a relational database  204 . The entities access relational data through data accessing system  206  which utilizes entity-relational (ER) map  208 . ER map  208  contains a mapping between the entities  202  and the table entries in relational database  204 . It should be noted that the present invention can be used in other systems, other than E-R systems, and the system shown in  FIG. 2  is but one example of a system in which the present invention can be used. 
     FIG. 3  is a unified modeling language (UML) class diagram of a customization framework  220  for a customization subsystem  222  in accordance with one embodiment of the present invention. Customization subsystem  222  is shown connected to a customizer user interface  224  which provides interaction between a customizer (such as a developer, user or intermediate customizer—e.g., a manager) and customization subsystem  222 . Subsystem  222  is also shown connected to a customization-enabled subsystem  226  which is, in turn, connected to a component  228  that is external to the customization features of the present invention. 
   Customizer interface  224  allows a customizer to access system  222  to make customizations to computer software, as will be discussed in greater detail below. The external component  228 , can be any component, such as a user, which desires to access some of the customized software. Customization-enabled subsystem  226  is any subsystem in the computing environment used by the user, which is configured to interact with the customization system  222  such that it can be customized. 
   Customization subsystem  222  includes an adapter system  230  and a target system  232 . Adapter system  230  is implemented with a base class SubsystemAdapter  234  and a plurality of data type adapters  236 ,  238 ,  240  and  242 . Target system  232  is implemented through a base class Target  244  and a plurality of data type targets  246 ,  248 ,  250  and  252 . Target system  232  is also in a composition relationship relative to a GeneratedAsset entity  254 . Both systems  230  and  232  have access to Context entity  256 . 
   Adapter system  230  operates as the primary connection point between customization-enabled subsystems  226  and framework  220 . Adapter system  230  implements customization logic that applies to the subsystem  226  as a whole. Target system  232 , on the other hand, contains logic which is used to customize specific instances of data types for which customization is desired. 
   Context entity  256  contains context information which identifies a current context. For example, it may be desirable to have customizations apply differently to people who play different roles at an organization. Similarly, it may be desirable for customizations to apply differently to different departments within an organization. Context entity  256  contains information which identifies a current context such that the customization associated with, and appropriate for, that context can be made. This is also discussed in greater detail below with respect to  FIG. 4 . 
   As is described below, framework  220  is extensible. For a subsystem to become customization-enabled, it must simply support the interfaces to framework  220 . To the extent that the subsystem has additional data types for customization, the only steps which must be taken are to provide an adapter (such as adapter  242 ) for the data types for which customization is desired. Similarly, the author of the subsystem must author a target (such as target entity  252 ). Together, the adapter and target entities have customization logic for customizing the subsystem as desired by the author of the subsystem. It will also be appreciated that such a subsystem can create additional customizer interfaces  224  through which users can create customizations of the subsystem&#39;s type. 
   In accordance with one embodiment of the present invention, software that may need to be customized includes several basic classes of content, which includes user interface content, data and process content. User interface content includes content that a user sees on a screen or report. It may contain such things as layout information, messages, field labels, etc. Data represents information that the system stores. For example, data includes customers, inventory items, orders, etc. Process content includes work flow specifications that route work through a defined set of steps, as well as lower level processing logic that executes well defined actions on a piece of data. An example of process content may include, for example, the work flow and lower level processing logic that posts an order to a ledger or reserves an inventory item. These types of content, as well as other types, can be customized in accordance with various embodiments of the present invention. 
   Regardless of the type of content to be customized, customizations may desirably be associated with a given context. Context governs when the customization is relevant. That is, the notion of a context allows some customization to only apply to a specific user, whereas other customizations apply to a whole set of users who belong to a specific group, and still other customizations apply to an entire company, without regard to users. These are but three different examples of context, and many others can be used as well. 
   Context entity  256  can be called by either adapter system  230  or target system  232  to obtain a current context.  FIG. 4  illustrates one embodiment of the data structures represented by context entity  256 . Of course, the context entity  256  represents data that is mapped into relational database  204 .  FIG. 4  illustrates one embodiment of tables which are used to identify which customizations apply to which context. 
   In the embodiment illustrated, context entity  256  maps to tables in relational database  204  that include a context table  257 , a customization table  259  and a customization-context table  261 . In the embodiment illustrated in  FIG. 4 , context table  257  includes fields that identify a context by a context identification number. Context table  257  shows four items of context including a user ID which identifies a specific user; a role which identifies a role within an organization, such as a manager, a sales person, a Vice President, etc.; an organization which identifies a business unit of a company, such as the shipping department, the sales department, etc.; and a locale which represents a geographic location. Of course, a wide variety of additional context elements can be used as well. 
   The first context entry in context table  257  indicates that the first context ID is associated with all managers in Europe. The second context ID is associated with a specific user having a user ID  12345 , and the third context ID is associated with managers in the shipping department. The customization table  259  includes an identifier associated with the different customizations that have been entered into the system, as well as the customization data that specifies the particular customization associated with that customization ID. The customization-context table  261  maps between context IDs and customization IDs. Therefore, customizations having the specified ID are applied to the various contexts identified in the associated context ID field. Of course, multiple contexts can be mapped to any given customization, and multiple customizations can be mapped to any given context. 
   Also, other table configurations can be used, and that shown in  FIG. 4  is but one example. For instance, table  261  can be eliminated and context table  257  can be provided with a customization ID field as well. There can still be many contexts for a single customization by having multiple rows in the context table. 
   In any case, systems  230  and  232  can request the current context from context entity  256  which can, in one embodiment, also return the identification of the particular customizations which need to be applied in the current context. 
   Entity Extension 
   In order to better illustrate the operation of the customization framework  220 , the discussion will now proceed with respect to  FIG. 3  in conjunctions with  FIGS. 5-6B . These Figures better illustrate customization of entities. This is also referred to herein as “entity extension”. 
     FIG. 5  illustrates data structures that are created when an entity in a customization-enabled subsystem is created.  FIG. 6A  illustrates the data structures that are shown in  FIG. 5 , in addition to data structures that are created, or modified, when an entity is customized.  FIG. 6B  is a flow diagram of how the entities in  FIG. 6A  are created or modified. 
     FIG. 5  shows a base entity  280  in a business application. The exemplary business entity  280  is a “customer” entity that identifies a customer in a business application. It will of course be appreciated that the specific examples illustrated are only examples and that the inventive concepts apply to other entities as well. Base entity  280  represents the entity being extended (or customized).  FIG. 5  also illustrates that base entity  280  is mapped to relational database  204  by the customer ER map entry  282  in ER map  208  (shown in  FIG. 2 ). A relationship between base entity  280  and other entities is identified in customer EA (entity association) map  284 .  FIG. 5  further illustrates that relational database  204  illustratively includes a customer table  286  associated with customer entity  280  that includes a customer ID field, a name field, an address field, and any other fields desired for identifying a customer. 
   Since the present invention does not require source code modification in order to customize entities, base extension entity  288  is also provided to enable the dynamic addition of new entity relationships to the base entity without recompilation of the base entity  280 . A base extension entity  288  is created for each base entity  280  that is created. Base extension entity  288  illustratively includes the name of the base entity  280  such that, in the present example, base extension entity  288  is named “CustomerExtension”. Base extension entity  288  is initially empty but can include a customer extension E-R map  290  and a customer extension EA map  292  which will also be empty. Base entity  280  contains a composition field that identities the base extension entity. For instance, base entity  280  can include a composition field named “Extension” of the type “CustomerExtension”. Entity association metadata for the Customer entity  280  reflects a relationship with the CustomerExtension entity  288 . Both entities  280  and  288  are illustratively shipped and deployed as DLLs when the product in accordance with the present invention is installed. Generation of these entities and the associated maps is indicated by blocks  400  and  402  in  FIG. 6B . At that point, a customizer can begin adding extension properties to the Customer entity  280  through a customizer user interface, such as interface  224  shown in  FIG. 3 . 
     FIG. 6A  illustrates how the extension properties will be added. Customizer interface  224  includes a user interface (UI) that calls into framework  220  with a list of new properties to be added to an identified entity. The specification of the new properties to be added is passed into entity extension target  246  where it is stored. The customizer can also identify the particular context that is stored in context entity  256  for which the particular customization is to be applied. Specifying the customization is indicated by block  404  in  FIG. 6B . It will also be appreciated that the context can be set at different times by different customizers. If the customizer is a developer, context can be set at the time of development. If the customizer is an administrator, context can be set as part of an administrator&#39;s function. In any case, the context is eventually set. 
   In order to make the customization active, subsystem  226  first calls the PreInstall( )method on subsystem adapter  234  to perform any processes required for subsystem  226 , as a whole, prior to installation. The subsystem  226  then invokes the ApplyCustomizations( ) method on EntityExtensionAdapter  236 . In response, EntityExtensionAdapter  236  then uses data accessing system  206  (shown in  FIG. 1 ) to identify the EntityExtensionTarget instance  246  that contains the customized properties. EntityExtensionAdapter  236  then calls Install( ) on the particular EntityExtensionTarget  246 . This is indicated by block  406  in  FIG. 6B   
   This causes EntityExtensionTarget  246  to create a new entity which is referred to as an ExtensionEntity. Two ExtensionEntities  300  and  302  are illustrated in  FIG. 6A . Each ExtensionEntity  300  and  302  includes at least one Extension property  304  and  306 , respectively, that identifies the customized property.  FIG. 6A  illustrates an embodiment in which customizations have been made by two different customizers, labeled customizer XYZ and customizer ABC. Therefore, ExtensionEntity  300  is illustratively named XYZ.CustomerExtension and ExtensionEntity  302  is illustratively named ABC.CustomerExtension. 
   By way of example, assume that customizer XYZ desired to customize the customer entity  280  to include an identification of a technician which was preferred by the customer identified by entity  280 . In that case, XYZ.CustomerExtension entity  300  includes Extension property  304  referred to as the “preferred technician property”. Similarly, assume that customizer ABC desired to customize the customer entity  280  to include a credit limit associated with the customer identified by entity  280 . In that case, ABC.CustomerExtension entity  203  includes Extension property  306  which identifies a “credit limit” associated with the given customer. 
   Not only does EntityExtensionTarget  246  create the ExtensionEntities  300  and  302 , with their corresponding Extension properties  304  and  306 , but it also illustratively creates E-R maps  310  and  312  and E-A maps  314  and  316 , respectively, corresponding to each of the ExtensionEntities  300  and  302 . In addition, EntityExtensionTarget  246  creates a table in relational database  204  (such as through data accessing system  206 ) that corresponds to the ExtensionEntities  300  and  302  and the other associated data structures. This is indicated by block  408  in  FIG. 6B . 
   Finally, base ExtensionEntity  288  is recompiled and its E-R map is regenerated to reflect the new relationship with the ExtensionEntities  300  and  302 . Similarly, E-A metadata is generated to reflect the new relationship with the ExtensionEntities as well. This is indicated by block  410  in  FIG. 6B . This can be done, for example, by calling the PostInstall( ) method on the EntityExtensionAdapter class. In this way, the recompilation includes both changes from ABC and XYZ. This could also be done on install of a given target but would require the entity to be re-compiled n times, once for each target. 
     FIG. 6A  also illustrates a plurality of different exemplary ways in which the database schema can be implemented to reflect the entity extensions made. In a first embodiment, the entity extensions are stored in the table illustrated as  320  in  FIG. 6A . It can be seen that table  320  includes the original table  286  that stores data associated with customer entity  280 . The original table is simply extended to include a plurality of additional fields  322  and  324  which correspond to the entity extensions. To avoid name clashes, the names are preceded by the namespace of the author to ensure uniqueness. Thus, the original columns in table  286  are unmodified. Extensions are simply added to the original table which correspond to the entity extensions. 
   In a second embodiment, each of the entity extensions is stored in its own table. Those tables are indicated by numerals  326  and  328 , respectively. Of course, a different table can be created for each customization, or all customizations for a given customizer (ABC or XYZ) can be stored in a single table. 
   In accordance with a third embodiment, the customizations are both stored in a single table  330 . In table  330 , both the entity extensions “preferred technician” and “credit limit” are stored in table  330 . In this embodiment, the column names are preceded with the namespace of the author to ensure uniqueness. Of course, table  330  could be enlarged to include all customizations for all entities, or all customizations for a single entity. In the latter case, a new table is created for each entity, that holds all customizations for that entity. 
   In accordance with yet another embodiment, the present invention can be used with a system in which one or more tables containing customizations have already been created, and thus already exist in relational database  204 . In that embodiment, the ExtensionEntities  300  and  302  are simply mapped to the already-existing tables that contain the customizations. 
   Entity extension can also be used to customize relationships among entities, and this is illustrated in  FIG. 6C .  FIG. 6C  shows an embodiment in which a customizer did not write the “Preferred Technician” customization as a string name in a simple field, but instead authored it as another entity  301  with associated maps  303  and  305 . In that case, customization takes place by adding an EA metadata relationship between the CustomerExtension entity  288  and the Preferred Technician entity  301  in the corresponding EA maps. 
   Metadata Customization 
     FIG. 7A  illustrates a metadata structure and metadata customization referred to herein as “delta-based customization”. The metadata structure in  FIG. 7A  is illustrated by a portion of a metadata structure tree  500 . It will be appreciated that the portion of tree  500  shown in  FIG. 7A  is illustratively but a very small portion of a much larger tree that defines metadata for the system. The portion shown in  FIG. 7A  illustrates that the metadata includes a Form section which itself includes a Customer_Maintenance_Screen. The Customer_Maintenance_Screen includes fields which have a plurality of Tab controls. Tab control  1  has a Field  1  associated with it. Field  1  has a plurality of properties, including the field name, the background color for the field, whether the field is enabled or disabled, the length of the field, and the data type for the field (which in this case is MaxValue). Of course, the field can have a plurality of additional properties as well. Metadata structure  500  is stored in a metadata store. 
   In order to customize a metadata structure  500 , the customizer inputs the customization specification through customizer interface  224 . This causes code to be included in MetadataTarget entity  248  that will apply customizations in certain contexts. 
   In an embodiment of the present invention, customization of all types of metadata in data structure  500  is achieved by using deltas. A delta represents a change in the metadata structure  500  from its original form. A customization can contain any number, n, of deltas, each delta representing a specific change relative to a known instance of a base target. Further, the delta need not simply represent a change to an existing node. Instead, the delta can represent the addition of a new node in the metadata structure  500 . In that case, the delta contains a reference to a parent node that it is to be a child of and a reference to a sibling node that it is requesting to come after. If two customization deltas have requested to come after the same sibling node, one will be placed before the other. This can be done in any desired way, such as arbitrarily, deterministically, or through conflict resolution (described below). 
   As an example of changing a value, in the original data structure  500 , the background color for the field having a name “foo” is yellow. Assume that a customizer wishes to change the background color to blue. In that instance, the customizer will have made a single customization containing a single delta. The customization is relative to the field “foo” under Tab  1  of the Customer_Maintenance_Screen. The customization can be stored in a separate part of the metadata store or in a metadata customization entity  502  which is mapped to the relational database  204 . A table in relational database  204  that can form a part of the metadata store is illustrated by table  504  which contains a metadata ID identifying the background color property of field  1  under tab  1  of the fields in the Customer_Maintenance_Screen portion of the Forms. Table  504  also includes delta information which identifies the delta, that being that the background color of the field is changed to blue. Thus, the delta is not a copy of the source that has been modified. Instead, it is only a specification of which value in structure  500  should be modified. By only tracking deltas, it is possible for many modifications to be dynamically applied to a target. 
   In order to apply the deltas, the customization-enabled subsystem  226  calls adapter  234  to apply customizations through MetadataAdapter  238 . MetadataAdapter  238  calls Apply( ) on MetadataTarget  248  to apply customizations in the present context. For instance, assume that customization-enabled subsystem  226  is the Form loading subsystem. Further assume that a user has requested the Customer_Maintenance_Screen to be displayed. Of course, MetadataAdapter  238  then identifies all MetadataTarget instances in the relational database that apply to the current context for the form named Customer_Maintenance_Screen. The MetadataAdapter  238  then calls MetadataTarget.Apply( ) on MetadataTarget  248  for each instance identified to apply the customizations. It can be seen that the customization to be applied to the metadata requires that the background color of Field  1  under Tab  1  of the Customer_Maintenance_Screen be changed to blue. The code in the MetadataTarget  248  makes this change and the customized portion structure  500  is passed back to the customization enabled form loader  226  for use in rendering the screen. 
   In accordance with one embodiment, the present invention also includes a mechanism to resolve conflicts where multiple deltas from different customizations reference the same property. For example, assume that a manager had customized the background color for the given Field  1  under Tab  1  of the Customer_Maintenance_Screen to be orange. Further assume that an employee had a personal preference customization changing the background color to blue. These two separate customizations both apply to the individual user. The individual user is part of the department for which the customization to orange has been made, but the individual user has, himself, made a customization to blue. These two customization instances are therefore in conflict. Both customizations are attempting to set the background color for the same field to a different color. However, a field can have only one setting for values such as color. Therefore, one customization must prevail, and the other must not. 
   In accordance with one embodiment of the present invention, customization conflicts are resolved using conflict resolution policies. Such policies are illustratively stored in a table which identifies a certain policy that applies to each of the different data types in metadata structure  500 . A portion of such a table is illustrated as table  510  in  FIG. 7B . Of course, table  510  is exemplary only. Table  510  includes a data type field identifying data types in structure  500  and a policy field indicating the conflict resolution policy to be applied. In one illustrative embodiment, the conflict resolution policies include the following:
         1. Most restrictive value;   2. Narrowest context;   3. Set once values;   4. Additive; and   5. Administrative override.       

   The most restrictive policy can be used for enumerations. For example, if one customization indicates that values A-E are valid and another indicates that values C-F are valid, then only values C, D, and E are valid because that is a most restrictive combination of the two conflicting customizations. This policy can also be used for numeric fields. For example, if the data type is a maximum value data type and two customizations attempt to set a number to two different values, then the minimum value is the most restrictive and prevails. If the data type is a minimum value data type, then the maximum value is most restrictive and prevails. 
   The narrowest context policy resolves conflicts in favor of the customization that is associated with the narrowest context. For example, a customization targeted at a single user would win over a conflicting customization with a corresponding context set to all users. 
   The set once values policy resolves conflicts such that a value can only be set once. It cannot thereafter be changed. 
   The additive policy applies to data types such as field groups (or groups of fields that will show up on a screen). A field can illustratively belong to multiple groups. Therefore, if one customization adds a field to a first group and another customization adds the same field to a second group, then the conflict is resolved by adding the field to both groups. 
   A final conflict resolution policy is administrative override. This allows an administrator to override conflict resolution policies on an item-by-item basis. 
   Of course, the conflict resolution policies are illustrative only and other or different policies can be used, as desired. 
     FIGS. 8A-8C  illustrate an even more concrete example of how customizations can be performed through entity extension. In the example illustrated in  FIGS. 8A-8C  assume that a car dealership Mortens Autos purchases a financial software package. After installation and running of the package, Mortens Autos customizes the product to add fields to track each customer car preferences (such as color, engine, make/model, etc.). Assume that Mortens Autos also adds new fields to a customer screen for the customer car preferences, and removes a number of unused fields. 
     FIG. 8A  illustrates a screen shot  450  of a standard customer screen displayed by the financial package purchased by Mortens Autos. It can be seen that screen  450  includes order summary fields which are not generally used in the car dealer industry.  FIG. 8A  also shows the same customer screen after the customizations have been implemented. The original order summary fields have been replaced with fields indicating the customer&#39;s last purchase and last purchase date. In addition, a car preferences tab has been added to display the customer&#39;s car preferences. This is all accomplished simply by extending entities and metadata as discussed above. 
   Next, assume that another solutions provider, Consoto, introduces electronic mail notifications for service reminders. Assume further that the customer entity provided by Consoto also adds a string to the customer entity for the name of the customer&#39;s favorite technician and a text box for a new field to the customer screen. An example of Consoto&#39;s customer screen is illustrated in  FIG. 8B . Assume that Mortens Autos buys, from Consoto, a software package to run the service department. 
   After the installation, all previous customizations still work without manual intervention or rework. This is shown in  FIG. 8C . For instance, the customer&#39;s car preferences field is shown on the screen and the original Order fields are removed from the screen. Similarly, Consoto&#39;s changes to the customer screen are also provided. Specifically, the new fields on the customer entity and text boxes on the customer screen are included. As is described above, when the new software package is installed, the customization subsystem framework is called and the customizations are installed and applied, automatically, without user intervention. 
   Customization of Processes 
   Processes typically include work flow specifications that route work through a defined set of steps, as well as lower level processing logic that executes well defined actions on a piece of data. Processes are referred to herein as business activities which can be long running business processes. 
     FIG. 9  further illustrates how a business activity  600  can be implemented. In one embodiment, the business activity  600  is broken into a plurality of individual transactional steps referred to as business operations. Each of the business operations that make up a business activity can be categorized into one of two different types of operations. The first is referred to herein as a planned operation replacement. In other words, when the original application developer plans on logic replacement, the application is written such that it selects the specific logic to execute at run time. In this way, third party developers may extend the type of processing that is done. The original author develops a “plug point” and one or more default implementations. Third party developers can then create and install additional implementations. The application typically provides storage in the application database for the selection of which business operation to execute in a given instance. An example of such logic is a sales commission calculation engine. The original author may build commission selection information into the SalesPerson entity, and might also supply a “fixed percentage” default. Of course, third party developers might create and install more sophisticated calculators. 
   A second type of business operation is referred to herein as an adhoc operation replacement. For instance, there are times when the original author does not plan on an operation being replaced. Therefore, the author may not build any special logic into the application to select an alternative implementation. However, a vendor may still need to replace the original operation with logic of its own. In order for the vendor operation to be called instead of the original operation, a framework mechanism is provided to modify selection logic. 
   Before describing these mechanisms in further detail, another concept should first be described. Business operations in accordance with one embodiment of the present invention, follow an agent-service pattern. A business operation agent is the only part of the process that a client directly interacts with. A client that needs to run the business process creates an instance of a business operation agent and sends it properties to provide its required inputs. In turn, the agent locates a corresponding service class (through a service factory), instantiates it, and calls it to actually perform the work that implements the service. 
   In either of the replacement scenarios mentioned above, the agent itself is not replaced. The client always creates and calls the same original business operation agent. This ensures that the client is always able to call the agent because it will have a stable interface. Business operation agents are entities and can have extension entities associated with them which can have additional properties added to them. This provides agent extensibility without breaking the original agent interface contract. The agent may locate the correct service to run in a number of different ways. 
     FIG. 9  further illustrates that business activity  600  is implemented using three business operations, operations  1 ,  2 , and  3 . Business operation  1  has an agent  602  and a business operation service factory  604 . Business operation  2  also has an agent  606  and a service factory  608 . Business operation  3  also has an agent  610  and a business operation service factory  612 . 
   For planned replacement, the calling application (or client) passes a service ID into the agent currently being called. The service ID indicates which service to activate. Thus, if the caller passes agent  602  a specific service ID, agent  602  identifies, through service factory  604 , the business operations service  614 , instantiates it, and calls it to perform the operation. Simply by passing in a different Service ID, the service can be changed. 
   For an adhoc replacement, there are two different methods that can illustratively be used in order to override the built-in selection of the business operation service. For example, assume that business operation  3  is to be replaced. In one embodiment, the service ID is stored in a metadata structure, such as that shown in  FIG. 10 .  FIG. 10  illustrates a portion of a metadata structure  625  which includes an item of metadata referred to as Operations. The Operations include three business operations, each of which includes a plurality of properties, one of which is the service ID. In that instance, the vendor can simply customize the portion of metadata which holds the service ID for the business operation to be overridden. 
   For example, assume that the service ID for business operation  1  is customized to instead be the service ID for a business operation number  4 .  FIG. 10  shows a table  627  referred to as the business operation customization table which includes a metadata identifier (the identifier for the service ID entry in the metadata structure) and the delta which shows the customization of the service ID to the number  4 . When the customizations are applied to this process, the service ID number  1  will be replaced with the customized service ID number  4 . This will be handed to the business operation service factory being used and it will instantiate and call business operation service number  4 . The agent will not pass any service ID to its factory, and the factory will then proceed normally to look up the associated default service ID in the metadata store. This will retrieve the customized service ID and the factory will instantiate the replacement business operations service instead of the originally designated service. Of course, this can be used to change an existing service ID or add a service ID where none existed before. 
   Another method to implement adhoc replacement customization is also illustrated in  FIG. 9 . In that embodiment, the particular service factory being utilized propagates an event. The vendor who wishes to customize the service operation can subscribe to this event and place logic in an associated event handler to alter the value of the service ID. This method not only allows customization of the business operation, but allows dynamic service selection based upon data contained in the business operation agent. For example, as shown in  FIG. 9 , business operation service factory  612  can propagate an event  622  when agent  610  calls factory  612  to instantiate a business operation service. The custom logic added to the associated event handler can alter the value of the service ID and pass it back to factory  612 . If the custom event code does not choose to set the service ID, the default (and potentially customized) value of the service ID is read from the metadata storage. 
   Dependencies 
   It is also worth noting that one embodiment of the present invention enforces customization dependencies. In other words, if one vendor or manufacturer customizes and ships a product and the user further customizes the product, customizations of items of data may depend on previous customizations of the same data. Thus, the base class of the customization framework maintains a list of what customizations are dependent on which other customizations. If a customizer wishes to create or remove a customization, the base Adapter class first determines whether other customizations depend on it. Each customization thus has an associated dependency list. In the adapter system, a method is called to enforce dependencies that will make certain that the customizer has affirmatively dealt with all dependencies prior to making customizations. 
   Although the present invention has been described with reference to particular embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.