Patent Publication Number: US-7917538-B2

Title: Method and apparatus for data item movement between disparate sources and hierarchical, object-oriented representation

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 10/299,456, filed Nov. 18, 2002, which is a continuation of U.S. application Ser. No. 09/132,813, filed Aug. 12, 1998, now U.S. Pat. No. 6,499,036 B1, issued on Dec. 24, 2002. All of these applications are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to data processing systems; in particular data processing systems using object-oriented computer programs to access managed data. 
     2. Description of Related Art 
     Large, modern business organizations are in a constant state of flux. The makeup of the business organization changes with every merger, acquisition, and divestiture. Related data assets come and go accordingly. The rapid pace of change represents a difficulty in keeping enterprise computer applications in synchronization with the changing set of disparate data sources with which they may be forced to contend. 
     Modern business enterprises face another challenge in matching their computer applications to their data assets. The majority of data assets are maintained using traditional data management systems and techniques. Some reasons for this are the huge investment made in building and maintaining the existing assets, the proven reliability of the existing systems, and the cost of migrating to more modern systems. Object oriented databases are on the horizon, moving from the laboratory to the field, but have yet to make serious inroads to widespread moving from the laboratory to the field, but have yet to make serious inroads to widespread commercial use. But while structured data management systems have lagged in adopting an object-oriented design paradigm, commercial application software designs have fully embraced it. Use of object-oriented programming languages, such as C++ and Java proliferates. Thus, modern business organizations face a schism between the design paradigm underlying their application software and the design paradigm managing the data on which the software is to operate. 
     Attempts have been made to bridge the gap between legacy data management systems and object oriented programs. U.S. Pat. No. 5,499,371 (Henninger), for instance, discloses method and apparatus for automatic generation of object-oriented source code for mapping relational data to objects. The invention of Henninger can greatly speed the work of a programmer by automatically generating source code that supports a fixed correspondence between object classes of the source code and the data fields managed by a traditional structured database system. The resultant source code is combined with other source code created by the programmer and compiled into an executable computer program. Changes at the structured database can, however, necessitate regeneration of the object class source code and recompilation of every program in which it is incorporated. This threatens a software maintenance burden to the dynamic business organization. Consequently, there is a need in the art to bridge the gap between the multiple, disparate, and ever-changing data sources of a business and its object-oriented application software, while minimizing the impact of, and maximizing the flexibility in responding to, changes in the data source makeup. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to the movement of data between multiple, disparate data sources and the object-oriented computer programs that process the data. A data access server is interposed between the object-oriented programs and the data sources, and acts as an intermediary. The intermediary server receives requests for data access from object-oriented computer programs, correlates each request to one or more interactions with one or more data sources, performs each required interaction, consolidates the results of the interactions, and presents a singular response to the requesting computer program. The consolidated response from the intermediary server contains data items requested by the computer program, information regarding the hierarchical topology that relates the data items, and an indication of the possible object types that might embody the data items. The application program receives the consolidated response and builds an object hierarchy to embody the data items and to interface them to the rest of the application program. 
     The class of an object used to embody data items is selected at execution time from a list of possible candidates. The same data access request, made by the same program, on two different occasions could result in objects of different classes being used to embody accessed data items because of a change in the data available over time. 
     A configuration database stores information about the types of data access requests that application programs can make to the intermediary server, the data sources with which the intermediary server interacts, and the types of interactions that are possible. The user of a computer program with a graphical user interface maintains the contents of the configuration database. The configuration database may include procedural scripts that permit detailed and conditional control over the work performed by the intermediary server to satisfy a data access request. 
     Embodiments employing the present invention may permit an application program to progressively augment a programming object with data items retrieved over multiple data access requests to the intermediary server. Moreover, the process of augmentation may result in some embodiments in the mutation of the underlying object from one class to another. In this way, the set of behaviors for a programming object can adapt to match the set of data items the object contains. 
     These and other purposes and advantages of the present invention will become more apparent to those skilled in the art from the following detailed description in conjunction with the appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts an operational overview employing the invention. 
         FIG. 2  depicts an operating environment for the present invention. 
         FIG. 3  depicts a general purpose computing platform for the practice of the invention. 
         FIG. 4  depicts a functional architecture employing the invention. 
         FIG. 5  is a flowchart showing the implementation process for one system employing the present invention. 
         FIG. 6  illustrates the main screen display of a GUI-based configurator program. 
         FIG. 7  illustrates the configuration of a transaction monitoring software system (CICS-EPI) used as a data source. 
         FIGS. 8 through 10  illustrate the configuration of SS transactions between a DOM server and a CICS-EPI data source. 
         FIG. 11  illustrates the configuration of a relational database management software system (RDBMS) used as a data source. 
         FIG. 12  illustrates the configuration of a session definition as may be required by RDBMS software. 
         FIG. 13  illustrate the configuration of an SS transaction between a DOM server and an RDBMS data source. 
         FIGS. 14 through 15  illustrate the configuration of a CS transaction between a client application program and a DOM server. 
         FIG. 16  illustrates a screen display for viewing configuration data in test format. 
         FIG. 17  is a flowchart showing the execution process for one system employing the present invention. 
         FIG. 18  depicts the layout of a data stream for communication between client and server. 
         FIG. 19  is an object diagram of example programming objects used to relate and embody data items in a client application program. 
         FIG. 20  is an interaction diagram showing an example of the processing in a client application program to request and objectize data items. 
         FIG. 21  is a flowchart showing an object-type selection process. 
         FIG. 22  is a class diagram including a folder class and family registration data. 
         FIG. 23  is a flowchart showing an alternative object-type selection process. 
     
    
    
     Where the same element appears in more than one figure, the same number designates the element is each figure. 
     DETAILED DESCRIPTION 
     Operational Overview 
     The present invention is useful in moving data items between their locations in permanent storage and locations in temporary storage where they can be manipulated by user application programs. Permanent storage, also known as persistent storage, maintains data over time, i.e., from one computing session to another. Permanent storage in a computer system may physically reside on mass storage devices such as magnetic disks. Temporary storage, also known as transient storage, maintains a data item for the time that it may be actively used and manipulated by an executing computer program. Temporary storage in a computer system may reside in the main memory devices of a computer such as DRAM integrated circuits, well known in the art. User application programs contain computer instructions in a logical arrangement that carries out the data processing work required by the user. 
     A modern user application program seldom contains the specific computer instructions to directly access data items on the physical storage devices where the data items permanently reside. Rather, a modern user application program invokes the execution of computer instructions contained in external software, such as an operating system or database manager, to mediate between a copy of the data item in permanent storage and a copy of the data item stored in temporary storage for the particular benefit of the user application program. 
       FIG. 1  depicts the conceptual operation of data item movement between persistent and transient storage utilizing the present invention. Data items in  FIG. 1  are depicted as circles, e.g.,  192 . A data item is the value stored in a field. Fields in  FIG. 1  are depicted as the rectangular boxes, e.g.,  191 , that immediately surround data items, e.g.,  192 . A field is a physical unit of data designated to contain a value having a certain meaning. To illustrate, five contiguous bytes of permanent storage may be designated to contain a postal code and may presently store the value “94105”. In this example, “94105” is the data item, and the five contiguous bytes are the field. A field may also comprise certain inherent or ascribed attributes, such as type, length, and data format. In the previous example, “postal code” is the field type, 5 bytes is the field length, and “numeric” is the field data format. The attributes of a field may apply equally to a data item stored in the field. For example, the “94105” data item has a length of 5 bytes. 
       FIG. 1  depicts that, by operation of data movement employing the present invention, a client computer  120  executing a user application program may have a transient working copy of a data item, e.g., A 1  embodied by an object-oriented programming object  160 . The persistent copy of data item A 1  is maintained in a persistent storage record  172  by external software, e.g., Data Source A. 
     More specifically,  FIG. 1  depicts that a plurality of transient data items embodied by programming objects  160 - 164  on client computer  120 , are persistently maintained by multiple independent data sources  172 - 178 . Object  160  embodies data items A 1 , A 2 , A 4  and B 2 . Data items A 1 , A 2 , and A 4  are maintained in persistent record  172  by Data Source A. Data item B 2  is maintained in persistent record  174  by Data Source B. Object  162  embodies data items D 1 , D 2 , D 3 , and D 4  which are maintained in persistent record  178  by Data Source D. Object  164  embodies data items C 1 , C 2 , C 3 , C 4 , and C 5  which are maintained in persistent record  176  by Data Source D. In summary, 3 programming objects embody transient data items maintained among the persistent records of 4 different data sources; and a single object may embody transient data items from more than one data source, e.g., object  160 . It is noteworthy that the present invention imposes no rigid correspondence, e.g., one-to-one, between the data items from a single data source or data source record, and the data items embodied by a programming object. This represents an advantage of the present invention. 
     To mediate between the transient and persistent copies of the plurality of data items embodied by programming objects  160 - 164  and maintained by the plurality of data source computers  130 , client computer  120  engages in a single client-server (CS) transaction  150  with server computer  110 . (A transaction comprises the generation of a request by a service-requestor computer program, the sending of the request to a service-provider computer program, processing of the request by the service-provider to generate a response, and the sending of the response from the service-provider to the service-requestor.) Server computer  110 , processes the transaction request received from client computer  120  by engaging in a plurality of server-source (SS) transactions  182 - 188 . Server computer  110  thus acts as a data access mediator between a client application program and data sources. Server computer  110  processes the transaction request utilizing information loaded into memory from a configuration database  115 . Information from configuration database  115  permits interpretation of the CS transaction request and resolution to a corresponding set of SS transactions. 
     For example, consider the case where client computer  120  desires to retrieve data items illustrated for programming objects  160 - 164  from the data sources, i.e., to make an inquiry. Client computer  120  sends the request portion of a CS transaction  150  to server computer  110 . Server computer receives the request, and identifies and interprets it based on information contained in configuration database  115 . Information from configuration database  115  also informs server  110  as to the format of the response expected by client computer  120 . Server  110  prepares to generate the response by building data container objects  140 - 144  with a topology that corresponds to the response format. In the presently described embodiment, the data container and response format topology also corresponds to a topology of relationships between programming objects  160 - 164  that will embody the data items in the client computer  120 . 
     Program logic executing on server  110  resolves the request of CS transaction  150  down to atomic SS transactions  182 - 188 . Server  110  initiates SS transaction  182  by sending a request to Data Source A that will return data items A 1 , A 2 , and A 4  from persistent record  172 . Data Source A may generate a response to server  110  that contains all of the data items from record  172 , or only the requested data items. After Data Source A sends the response portion of transaction  182  to the server, program logic on server  110  will isolate the desired data items, i.e., A 1 , A 2 , and A 4 , out of the transaction  182  response and store them in container object  140 . Server  110  then repeats the process for each of transactions  184 ,  186 , and  188 , sending a request to the data source, receiving the response, and moving data items as necessary into the appropriate data containers  140 - 144 . 
     After the last SS transaction  188  is completed and its response data items D 1 -D 4  have been moved into data container  142 , server  110  transforms the data container contents and topology into a data stream. The resulting data stream is the response portion of CS transaction  150  that is sent from server  110  to client computer  120 . Client computer  120  receives the response data stream that consolidates the multiple SS transaction  182 - 188  responses from the disparate data source computers  130 . Program logic in software running on client computer  120  processes the data stream to extract the data items it contains and embody them in programming objects  160 - 164 . 
     In a preferred embodiment employing the present invention, programming objects  160 - 164  are constructed as a result of processing the response data stream for CS transaction  150 . The specific class used to instantiate a particular programming object is selected at instantiation time; i.e., dynamically during execution of the program and not statically during its development. (A class serves as the definitional model for the object to be created.) The class selected is determined by the field types of the data items contained in the response stream. For example, programming object  160  is instantiated from class “Customer” because of the field types associated with data items A 1 , A 2 , A 4 , and B 2 . If, for example, object  160  represents a banking customer, and data item B 2  contains the customer&#39;s password, and an inquiry transaction  184  fails because record  174  was previously deleted so that no password data item is sent to the client computer in response to transaction  150 , then programming object  160  may instantiate from the “UnsecureCustomer” class, rather than from the “Customer” class, because of the missing password data item. It is fundamental to object-oriented programming that the class of an object determines the properties it can maintain and the behaviors it can perform, which together determine its data processing characteristics. Instantiation under the UnsecureCustomer class could produce an entirely different set of behaviors for object  160  than instantiation under the Customer class, such as behavior that fails to authorize use of an automated teller machine. To pursue the example further, if transaction  150  occurs again for the same customer at a later time, and if record  174  had been restored in the meantime, then object  140  instantiates from the Customer class and normal ATM authorization resumes. The ability to determine object class at execution time based on the types of data items instantly available represents a further advantage of the present invention. 
     Operating Environment 
       FIG. 2  depicts an operating environment for the practice of the present invention. Operating environment  200  supports the creation and execution of user application programs that can access data from disparate sources through the unified interface provided by an intervening server as previously described in relation to  FIG. 1 . The operating environment  200  is split between a development portion  202  and an execution, or run-time, portion  204 . Development environment  202  includes developer workstation  260  and development files  250 . Developer&#39;s workstation  260  includes development software  262  and GUI-based configurator software  264 . Development files  250  includes libraries  252 . 
     Execution environment  204  includes data source computers  130 , server computer  110  and client computer  120 . Server computer  110  includes DOM software  210 . Client computer  120  includes application program  220 . Data source computers  130  include data access software (not shown). Application program  220  includes program instructions of an FDO component  222  and programming objects  160 - 164 . 
     Configuration database  115  and Application software  240  participate in both the development  202  and execution  204  portions of the operating environment  200 . Use of the development environment  202  generally precedes use of the execution environment  204 . The development environment  202  is used to create and maintain application software  240  and the configuration database  115 . The application software  240  and configuration database  115  created and maintained by utilization of development environment  202  are used in the execution environment to control operation of the client  120  and server  110  computers, respectively. 
     Developer workstation  260  is a general purpose computer such as a desktop personal computer. A software developer uses developer workstation  260  to execute GUI-based configurator software  264  to create and maintain the contents of configuration database  115 . The configuration database  115  contains information about how a client program  220  can request data services from the server  110 , and how the server  110  can fulfill those requests using the disparate data sources  130 . After knowing information loaded into configuration database  115 , an application developer can use workstation  260  to create client application programs that will carry out transactions with server  110  when executed. 
     A programmer uses development software  262  to create an application program that will run on a client computer  120 . Development software  262  may include source code editors, integrated development environments, language compilers, linkers, debuggers, and other tools used by programmers to develop software. In the preferred embodiment these tools support development in an object oriented language such as C++ or JAVA. Such tools are well known and understood in the art. 
     During the development process, the development software  262  creates, maintains, and uses various development files  250 . Development files  250  may include, for example, source code, object code, executables, and related files. Development files  250  may also include libraries  252  of the above types of files in a form intended for generalized or standardized use, e.g., subroutine libraries or graphical control libraries. Development files may be originally created by the user, or come from the operating system software provider, a software vendor, or from another source. The types of files  250  used in the development of application programs are well known and understood in the art. 
     At the culmination of the development process for an application program, development software  262 , such as a linker, creates a ready-to-use executable program  242  and stores it as application software  240 . 
     In a preferred embodiment, development files  250  includes libraries of generalized source code files. The files in the libraries define and implement classes and objects that, when compiled with user source code into a ready-to-use executable program  242 , effectuate a transmutation between data exchanged with the server  110 , and object instances  160 - 164  in a running copy  220  of the persistently stored executable program  242 . This transmutation process represents a further advantage of the present invention which is more fully discussed later in this detailed description. 
     Execution environment  204  is used to perform data processing desired by the user, for example, maintaining the user&#39;s customer accounts. Application software  240 , such as persistently stored executable program  242 , is loaded into client computer  120  to become executing program  220 . Executing program  220  contains instructions  222  that initiate and respond to formatted transaction data streams exchanged with data object manager (DOM) server software  210 . Notably, foundation for distributed objects (FDO) instructions  222  transmute between live programming objects  160 - 164  in executing program  220 , and the contents of a data stream exchanged with the DOM server software  210 . In a preferred embodiment, FDO instructions  222  result from program compilation in the development environment  202  using generalized source code files as contained in library  252 . 
     In one such exchange, the FDO instructions  222  may send a data stream to the DOM server software  210  executing on the DOM server computer  110 , that requests account data for a customer. DOM server software  210  receives the request, and interprets it based on information extracted from configuration database  115 . DOM server software  210  acts as a data access Mediator between application program  220  and data sources  130 . The interpreted request may resolve to one or more data requests sent to one or more of data sources  130 . This process is described earlier in relation to  FIG. 1 . 
     Data source computers  130  are representative of the disparate types of data sources that can be accommodated in an embodiment employing the present invention. Data source  130   a  is a computer running IBM&#39;s CICS software and implementing its external presentation interface (EPI). CICS is a distributed online transaction processing system including system controller and utility software components that can support a network of many user display terminals interacting with user-written transaction programs. The EPI interface component allows programs external to CICS to access CICS transaction programs by emulating a display terminal device and its operator. The external program “reads” the screen display information by analyzing the data stream sent by CICS. The external program communicates to CICS by generating a data stream that mimics the keyboard strokes that would be sent by a terminal operator. 
     Data source  130   b  is a computer running IBM&#39;s CICS software and implementing its external call interface (ECI). The ECI interface component of CICS is designed for program-to-program communication, rather than program-to-terminal communication. The ECI interface allows an external program to invoke a CICS-managed transactional program module and communicate with it via a formatted data area. 
     Data source  130   c  is a computer running messaging system software that acts as the broker for transferring data “messages” between sender and recipient software programs. Message server data source  130   c  can be thought of as an email system for computer programs. One example is IBM&#39;s MQSeries software which can transmit and receive messages between programs running on heterogeneous systems; i.e. systems comprising hardware and software from various vendors and usually employing a variety of operating systems, communication systems, and protocols. Message server  130   c  acts as a data source by providing a mechanism whereby a data-using program can invoke the services of a data-maintaining program, but the message server software does not necessarily itself maintain a repository of business data. 
     Data source  130   d  is a computer running an operating system that provides access services for rudimentary file structures such as flat files. An example is a POSIX operating system providing access to files formatted as a standard UNIX text file. 
     Data source  130   c  is a computer running relational database management system (RDBMS) software. RDBMS software provides services to external programs for creating and maintaining data collections using a relational model. The relational model is well known and understood in the art. Examples of RDBMS&#39;s include ORACLE and INFORMIX products. 
     Notably, the bulk of electronic data processing occurring in business today utilizes data sources as those mentioned above  130 . In addition to data, sources such as CICS systems  130   a - b  also embody the huge investment that has been made in application programming to capture and automate business logic (e.g., a transaction program running under CICS may perform many data processing operations other than merely retrieving or storing data such as editing, verifying, reformatting, accumulating, etc.). It is an advantage of an embodiment employing the present invention that the wealth of these legacy data sources can be accessed without any changes to the legacy system. This is possible because DOM server software  210  interfaces to each legacy data source using an interface standard defined by the data source, rather than one defined by the DOM software. It is a further advantage of the present invention that client programs can access this wealth of disparate data sources without each being aware of all of the details for accessing all of the available data sources, but can rather utilize the unified interface provided by the DOM server. 
       FIG. 3  depicts a general purpose computing platform for the practice of the invention. General purpose computer  300  comprises CPU  310 , signal bus  312 , memory  320 , mass storage  330 , input/output  340 , and data communication  350 . Input/output  340  comprises keyboard  342  and video display  344 . CPU  310  executes program instructions stored in memory  320  to process data stored in memory  320 , and to control and effect the movement of data between and among memory  320 , mass storage  330 , input/output  340 , and data communication  350 . Memory  320  may receive, store, and recall computer software and data in a series of storage locations directly addressable by CPU  310 . Example memory devices include ROM, RAM, DRAM, and SDRAM circuits. Memory  320  often comprises largely volatile storage devices, i.e., devices that retain their contents only so long as power is constantly supplied. Currently executing computer programs and transient business data are examples of computer software and data that are stored in memory  320 . 
     Mass storage  330  similarly may receive, store, and recall computer software and data, but is generally slower and of much greater capacity than memory  320 . Mass storage  330  generally comprises non-volatile, or persistent, storage devices. Mass storage  330  may comprise read/write and read-only devices. Example mass storage devices include those supporting and incorporating storage (recording) media such as magnetic disks, optical disks, magneto-optical disks, and magnetic tape. The storage media for the device may be fixed or removable. Program files, including operating system and application program files, configuration and management data files, and user data files are examples of computer software and data that reside on the storage media of mass storage  330 . 
     Input/output  340  provides for human interaction with computer  300 . Example input devices that allow a human operator to introduce data to signal bus  312  include keyboard, computer mouse, trackball, touch pad, digitizing tablet, and microphone. Example output devices that allow data from 312 to be presented to a human operator include video display, printer, and audio speakers. 
     Data communication  350  provides circuitry to exchange data on signal bus  312  of computer  300  with computers or other data devices attached to connection  352 . While Input/output  340  provides for interaction with a human operator, data communication  350  provides for interaction with other computers. For example, data present in computer  300  may be conveyed via data communication circuitry  350  to computer  360 , via connection  352  and network  354 . 
     General purpose computer  300  is representative of the computing devices illustrated in  FIG. 2  as Developer workstation  260 , client computer  120 , DOM server computer  110 , and data source computers  130 . 
     Architecture—Layered Design 
       FIG. 4  depicts a functional architecture employing the present invention. The described embodiment utilizes a layered architecture to mediate the end-to-end movement of data items. At one end is user application code  490  that manipulates a transient copy of a data item. At the other end are stored data  432  which contain persistent copies of data items. Intervening between the ends are a client transactor layer, a client-server (CS) communication layer, a server processor layer, a resource adapter layer, a server-source (SS) communication layer, and a data access layer. Client transactor layer comprises executing Foundation for Distributed Object (FDO) program code  450  that functions to interface user application code  490  to the request and response data formats and protocols required by the DOM server software  210 . CS communication layer comprises CS communication channel  460  that functions to transfer request and response related data bi-directionally between the client transactor layer and the server processor layer. Server processor layer comprises DOM core program code  410  that functions to receive, process, and respond to transaction requests originating from user application program code  490 . The server processor layer processes the requests it receives by initiating SS transactions with data sources  430 . Resource adapter layer comprises resource adapters  412  that function to receive SS transaction requests from the DOM core and to conduct the requested transaction activity with an associated data source on behalf of, and under the direction of, the DOM core. SS communication layer comprises SS communication channels  471  that function to transfer SS transaction request and response related data bi-directionally between the resource adapter layer and the data accessor layer. Data accessor layer comprises data accessor programs  431  that function to maintain and manage the persistent data items contained in stored data  432 . 
     It can be seen that a particular layer in a layered architecture can, itself, be divided into sublayers. For example, the CS communication layer comprises a proxy layer, a proxy-facade (PF) communication channel layer, and a facade layer. The proxy layer comprises protocol-specific proxy  452  that functions to interface the client transactor layer to the formats and protocols required by the particular PF communication channel in use. The PF communication channel layer comprises PF communication channel  462  that functions to transfer data bi-directionally between the proxy layer and the facade layer. The Facade layer comprises protocol-specific facade  414  that functions to interface the server processor layer to the formats and protocols required by the particular PF communication channel in use. 
     Computer elements depicted in  FIG. 4  underlie and form part of elements already described in relation to the layered architecture. Computer elements depicted in  FIG. 4  include client computer  120 , server computer  110 , and source computers  130 . Client computer  120  and server computer  110  each provides general purpose computing circuitry and support software to execute associated program code in the architecture. Source computers  130  represent general purpose computers corresponding to data sources  130  in  FIG. 2 . Each of source computers  130  provides general purpose computing circuitry and support software to execute associated program code in the architecture, e.g., data accessor programs  431 . 
     Other elements depicted in  FIG. 4  operate together with those already discussed to serve the overall objective of data item transfer between data sources and user application programs. These elements include process activation daemon (PAD)  416 , configuration database  115 , and execution processes  480 - 484  which are described in the detailed structural and operational description of the architecture that follows. 
     Architecture—Detailed Description 
     The operational overview described in reference to  FIG. 1  is repeated here with attention to the architectural components depicted in  FIG. 4 . Client computer  120  communicates with server  110  to gain access to persistent data maintained by data sources  130 . Client computer  120  executes client application program  220  comprising user application program code  490 , FDO program code  450 , and protocol-specific proxy  452 . Application program code  490  includes program objects  160 - 164 . Client computer  120  connects to server  110  via communication channel  460 . 
     DOM server computer  110  executes DOM server software  210  comprising the program code of process activation daemon (PAD)  416 , protocol-specific facade  414 , resource adapters  412 , and DOM core  410 . DOM server computer  110  connects to data sources  430  via communication channels  470 . DOM server software  210  executes using execution processes  480 - 484 . 
     Data sources  430  comprise the executing program code of data accessors  431 , and stored data  432 . A data source such as data source  430   a  comprises the executing program code of data accessor software  431   a , and the stored data  432   a  maintained by that code. A data source such as data source  430   a  corresponds to one of the data sources  130  depicted in  FIG. 2 . 
     User application code  490  includes program logic to carry out the specific data processing desires of the user. User application code  490  may include code to interact with the operator of client machine  120  via its input/output devices (see  FIG. 3 ). Possibly in response to user input, part of the program logic of user application code  490  directs utilization of data items maintained in data sources  430 . The program logic directing utilization of such data items connects to FDO program code  450 . 
     FDO program code  450  includes generalized program logic for communicating with the DOM server software  210 . The generalized program logic is tailored by development-time (e.g., compilation) or execution-time (e.g., variable assignment) processes to perform the instance-specific processing directed by the user application program  490 . 
     In the presently described embodiment, when sending a service request to server software  210 , FDO program code  450  transmutes programming objects, such as objects  160 - 164 , into a data stream for transmission to the server. In receiving replies to service requests from server software  210 , FDO program code  450  transmutes a data stream received from the server into programming objects such as objects  160 - 164 . The details of this transmutation process are fully described later in this detailed description. 
     FDO program code  450  connects to the program code of protocol-specific proxy  452  to begin the exchange of a data stream with server software  210 . Protocol-specific proxy  452  communicates with FDO program code  450  in a format used universally by FDO program code  450  to communicate with the CS communication layer elements of the architecture. This facilitates interchangeability of specific components occupying the CS communication layer in a specific implementation, particularly PSP  452 . Protocol-specific proxy  452  converts data streams and related request and control information between the common FDO program code format and the format required by the communication channel to which it is connected  462 . 
     Communication channel  462  connects protocol-specific proxy  452  to protocol-specific facade  414 . Communication channel  462  supports the bi-directional transfer of data. Communication channel  462  may comprise a physical communication medium interposed between support circuitry and software at each end. The channel  462  may provide for communication between programs executing on the same computer, or on computers located thousands of miles apart. Examples of communication channels that may be employed in the presently described embodiment include TCP/IP network connections, Common Object Request Broker (CORBA) facilities, and Distributed Component Object Model (DCOM) facilities. These and other inter-program interaction and communication vehicles are well known and understood in the art. 
     Protocol-specific facade  414  converts data streams and related request and control information between the format required by the communication channel  462  to which it is attached and a format useable by DOM core program code  410 . DOM core  410  communicates with protocol specific facade  414  in a format used universally by DOM core  410  to communicate with the CS communication layer elements of the architecture. 
     In the aggregate, protocol-specific proxy  452 , communication channel  462 , and protocol-specific facade  414  effectively form a client-server (CS) communication channel  460  between FDO program code  450  in the user application program and the core program code  410  of the DOM server  210  (i.e., the CS communication layer of the architecture). Furthermore, CS communication channel  460  in combination with the FDO program code  450 , together represent a client-server interface that connects user developed code  490  with the DOM core  410 . Program code implementing such client-server interface in an embodiment may advantageously adhere to an industry standard interface specification. For example, the FDO program code  450  on the client side of such a client-server interface could comply with an industry standard application programming interface (API) for data access such as open database connectivity (ODBC) or object linking and embedding (OLE). 
     DOM core program code  410  contains program logic to receive, process, and reply to requests received from client application program  220 . When DOM core  410  receives a request, it uses information in the request data stream sent by the client to determine the action required to satisfy the request based on information loaded into memory from configuration database  115 . The required action will resolve to one or more requests that need to be directed to appropriate data sources  430 , i.e., SS transaction requests. 
     For each SS transaction request that needs to be directed to a data source, the DOM core  410  connects to program logic in one of resource adapters  412  to initiate the transaction with the associated data source. As to transactions between the DOM server software  210  and the data sources  430 , the DOM server software acts as the client, and the data sources each act as a server. For example, the DOM core  410  connects to resource adapter  412   a  to begin an exchange with data source  430   a . Resource adapter  412   a  communicates with DOM core program code  410  in a format commonly used by all resource adapters  412 . Resource adapter  412   a  accepts requests in the common DOM format and perform is the requested transaction by communicating with data source  430   a  in accordance with requirements imposed by communication channel  471   a  and data access software  431   a.    
     Communication channel  471   a  connects resource adapter  412   a  to data access software  431   a . Communication channel  471   a  is a bi-directional data communication channel. Communication channel  471   a  may comprise a physical communication medium interposed between support circuitry and software at each end. The channel  471   a  may provide for communication between programs executing on the same computer, or on computers located thousands of miles apart. Examples of communication channels that may be employed in the presently described embodiment include TCP/IP network connection and SDLC network connections. These and other inter-program communication and interaction facilities are well known and understood in the art. 
     Data access software  431   a  contains program logic to receive, process, and reply to requests received from DOM core  410 . The requests received from DOM core  410  relate to accessing stored data  432   a  maintained by data access software  431   a . When data access software  431   a  receives a request from DOM core  410 , it interprets the request and may read, modify, insert, or delete certain contents of stored data  432   a  to satisfy the request. Data access software  431   a  also generates a response back to DOM core software, appropriate to the request. 
     Resource adapter  412   a  and communication channel  471   a  together operate as described above to give the DOM core access to data source  430   a . Resource adapter  412   b  and communication channel  471   b  operate similarly to give the DOM core access to data source  430   b . Resource adapter  412   c  and communication channel  471   c  operate similarly to give the DOM core access to data source  430   c . In the presently described embodiment there are only practical limits, such as memory and CPU capacity, restricting the number of data access pipelines  470  associated with an executing DOM server  210 . The ability of the DOM server  210  to simultaneously interact with multiple and disparate data sources represents a further advantage of the present invention. 
     The DOM server software  210  depicted in  FIG. 4  also includes process activation daemon (PAD)  416 . PAD  416  program logic loads and executes on server machine  110  to initiate operation of the DOM server software  210 . PAD  416  reads configuration information from configuration database  115 . Based on the information obtained from configuration database  115 , PAD  416  starts multiple processes  482 - 484 . Each process is viewed by the operating system software of server computer  110  as an independently manageable and dispatchable unit of work. PAD  416  starts processes  484 , and  482   a - c , to execute DOM core  314 , and resource adapter  412   a - c  program logic, respectively. Starting each process includes loading the program code that directs the execution of the process. For example, starting process  484  includes loading DOM core program code  410  from mass storage into main memory. 
     PAD  416  program logic also monitors ongoing operation of the processes it starts, and will restart any process that terminates in accordance with restart information contained in configuration database  115 . Such information may include, for example, an amount of time to wait before attempting a restart. In the presently described embodiment, PAD  416  also maintains a log file (not shown) where it records activity such as starts, terminations, and restarts of the processes it manages. 
     PAD  416  starts resource adapter processes  412   a - c , after starting DOM core process  484  is shown. In the presently described embodiment one process  484  executing DOM core program logic  410 . All inbound communication channels  462  from client machines, and all outbound communication channels  471   a - c  to data sources, connect to the single executing copy of DOM core program logic  410 . In other embodiments, multiple processes running DOM core program logic may be started on a single server machine  110 . Inbound requests from client machines and outbound requests to data sources may then be distributed among the multiple executing DOM core processes to manage or enhance performance. One skilled in the art recognizes that these and other variations can be made without departing from the scope and spirit of the invention. 
     Implementation Process 
     Because an embodiment practicing the invention can provide a generalized data access capability, the specifics of any desired data access operation must be declared for the DOM server and the client application program. This is the implementation process.  FIG. 5  is a flowchart showing the implementation process for one system employing the present invention. The implementation process prepares a data processing system to perform data accessing operations in accordance with the present invention. The implementation process occurs using the development environment  102  as described in relation to  FIG. 1 . 
     Steps  520  through  540  are performed using the GUI configuration utility described earlier. Steps  520  through  540  populate the DOM configuration database  115  which stores information used to direct the operation of the DOM server software during its execution. Step  520  records configuration information for the DOM server&#39;s Process Activation Daemon (PAD). Step  520  records its output in PAD Configuration file  572 , which is contained in configuration database  115 . PAD Configuration file  572  contains three sections. An ENVIRONMENT section contains information about the identity and location of computing resources on the server host. Such resources may include, for example, file directories or communication ports. RESOURCE ADAPTER and DOM sections contain information the PAD needs to start, control, and monitor resource adapter and DOM core processes. Such information may include, for example, a name that identifies a computer to run the process; an indicator whether restart should be attempted for a failed process; how many times, how often, and how long to wait for restart attempts; information the operating system should provide to the process if specifically requested; the command string to submit to the operating system to start the process; and the command string to submit to the operating system to restart the process. The RESOURCE ADAPTER and DOM sections may additionally include information to facilitate concurrent execution of multiple resource adapters or DOM cores on the server machine. Such information may include, for example, the number of DOM or resource adapter occurrences the PAD is to run. 
     Step  530  records configuration information used by executing resource adapters. DOM configuration “resources” as defined in step  530  refer to data sources. Each resource definition corresponds to a run-time resource adapter process and the SS transactions that the particular resource adapter can perform. The output of resource definition step  530  corresponding to a particular resource adapter goes to a particular resource adapter configuration file  574 . Resource adapter configuration file  574  is contained in configuration database  115 . Configuration database  115  in the presently described embodiment contains one resource adapter configuration file for each resource adapter specified in PAD configuration file  572 . 
     A resource definition contains information concerning the resource adapter. For example, such information may include the type of data source to which the resource adapter connects; location, authorization, and interface information used to establish secure and reliable communication with the data source; and process management information about the resource adapter such as the amount of time to wait for initialization, restart parameters, environment information such as file directory names, a shell command for starting the resource adapter, and whether multiple, concurrent copies of the resource adapter may execute. 
     A resource definition also contains information concerning each particular SS transaction that the related resource adapter can accommodate. For example, information about a transaction may include an identifier for the transaction type, parameters to control transaction execution, the format of the transaction request, the format of the transaction reply, the correspondence between transaction data items and DOM server data container data items, and procedural logic needed to conduct the transaction. Because different resource adapters can connect to different types of data sources, and because different data sources may each have their own particular defined interfaces, the specific information required to engage in a transaction may vary from data source type to data source type. In a preferred embodiment, each transaction definition corresponds to what the data source considers to be a single, atomic transaction. i.e., one request-process-reply sequence. The atomic transaction may also include required handshaking such as session set-up and tear-down. 
     “Methods” are defined in step  540 . DOM Configuration “methods” refer to CS transactions. Each method definition corresponds to a type of CS transaction that a user application program may engage in with the DOM server. The output of method definition step  540  goes to a DOM Configuration file  576 . DOM Configuration file  576  is contained in configuration database  115 . Each method definition contains information needed by DOM core software to identify, process, and respond to a CS transaction request from a client user application program. Information about a transaction may include, for example, an identifier for the transaction type, parameters to control transaction execution, the format of the transaction request, the format of the transaction reply, the correspondence between transaction data items and DOM server data container data items, and procedural logic needed to conduct the transaction. 
     At the completion of steps  520  through  540 , the DOM configuration database contains the information needed by DOM server software to manage its own operation on the server computer, define the data access transactions it will make available to its clients, and define the data access transactions it may conduct with data sources in order to satisfy client requests. Each of steps  520  through  540  must be conducted once before a fully functional DOM server can be executed using configuration database  115 . Each of steps  520 ,  530 , and  540  may then be repeated individually or in combination as needed to reflect additions or changes to the information contained therein. 
     Step  550  creates a client application program. The output of client program creation step  550  is an executable program  242  in mass storage that can be loaded and executed in a client computer. In a preferred embodiment, the client program is written by a computer programmer using an object-oriented computer language such as C++ or Java. The programmer includes source code in the program to send a request to a DOM server. The request is formulated to invoke a method defined in step  540 . The source code is compiled and linked to form executable program  242 . Application program  242  will control the operation of a client computer at execution time. After step  550 , the implementation process is complete. 
     GUI-Based Configuration 
     The implementation process described in relation to  FIG. 5  begins by loading configuration information into files in a DOM configuration database. The files comprising the DOM configuration database in the presently described embodiment are stored in a text format. This format represents a compromise between a format optimized for human readability and a format optimized for machine readability. Storage of configuration files in text format permits a user to maintain the configuration files using any of the readily available text editor programs available on the particular server platform. Maintenance of the configuration files using a text editor is, however, error prone, and requires the user to have detailed knowledge about the many files that together comprise the configuration database. The presently described embodiment includes graphical user interface (GUI) based configurator software to provide easier, more understandable, less error-prone maintenance of the configuration database. The GUI-based configuration is described in relation to  FIGS. 6 through 16 . 
       FIG. 6  illustrates the main screen display of a GUI-based configurator program. Such a GUI-based configurator program may run, for example, under the Windows NT operating system from Microsoft Corporation. Main screen display window  600  comprises title bar  610 , menu bar  620 , tool button bar  630 , status bar  640 , methods display area  650  and resources display area  660 . Windows, title bars, menu bars, tool button bars, status bars, and display areas are well known and understood in the art. 
     The leftmost portion of title bar  610  identifies the window as belonging to the DOM Configurator software. The rightmost portion of title bar  610  includes customary window control buttons to invoke window minimization, window maximization, and termination processing for the configurator program. 
     Menu bar  620  displays “File,” “Edit,” and “Help” options. Each menu option, when selected by a keyboard or pointer device, displays a list of functions that the user can perform using the configuration software. Functions listed under the File menu option principally relate to storing and loading configuration database information to and from mass storage devices. Functions listed under the Edit menu option principally relate to modifying configuration information that is graphically depicted as the visible content  652 ,  662 ,  664  of the method and resource display areas  650 ,  660 . Functions listed under the Help menu option principally relate to displaying information about the DOM configurator software and its use. 
     Tool button bar  630  depicts an array of graphical icons, each of which may be selected by the user using a pointing device to invoke certain processing by the configurator program. An icon displayed on tool button bar  630  may correspond to a particular function in the list associated with a menu bar option. For example, a tool button bar  630  icon may invoke the same processing to save configuration information on a hard disk, as does a menu option listed under the File option of the menu bar  620 . A tool button bar  630  may include icons to invoke processing that creates a new configuration, loads an existing configuration from mass storage, stores a configuration to mass storage, presents a dialog window with which to edit PAD configuration file data, displays configuration data in text format, exchanges data with a clipboard facility, adds or deletes a configuration element in a display area (and its underlying data), presents a dialog window with which to modify the data underlying a configuration element, displays helpful information, or that finds and highlights a particular configuration element. 
     Status bar  640  may display such information as the name and location of a configuration file on mass storage associated with the display contents  652 ,  662 ,  664  in method and resource display areas  650 ,  660 . Status bar  640  may also display the current date and time-of-day. 
     Method display area  650  graphically depicts the configuration information associated with any DOM configuration file in a configuration database. This information defines and describes the client-server (CS) transactions available to a client application program through a DOM server. Resources display area  660  graphically depicts the configuration information associated with any resource adapter configuration file in a configuration database. 
     The visible contents  652 ,  662 ,  664  in the display areas  650 ,  660  shown in  FIG. 6 , and described in more detail in subsequent figures, illustrate one way to configure the operating example depicted and discussed earlier in relation to  FIG. 1 . The chief difference between the operating example of  FIG. 1  and the configuration example of  FIG. 6  (and subsequent figures) is that the four data records  172 - 178  of  FIG. 1  come from two data sources in the configuration example of  FIG. 6 , rather than from four data sources (A-D) as shown in  FIG. 1 . 
     Resource (SS Transaction) Configuration. 
       FIGS. 7 through 13  illustrate GUI configuration for resource adapters and SS transactions.  FIGS. 7 through 10  illustrate GUI configuration for a CICS-EPI resource and three associated SS transactions.  FIGS. 11 through 13  illustrate GUI configuration for an RDBMS resource and one associated SS transaction. The configuration activity represented by  FIGS. 7 through 13  corresponds to the activity represented by step  530  of  FIG. 5 . 
       FIG. 7  illustrates the configuration of a transaction monitoring software system (CICS-EPI) used as a data source. The “EPI (CicsEpi)” element  791  of the visible contents  662  from the resource display area ( 660  of  FIG. 6 ) of the DOM Configurator main screen ( 600  in  FIG. 6 ) represents the configuration information for a CICS-EPI data source  130   a . After adding element  791  to the resource display area, the user of the DOM Configurator displays dialog box  700  to view and modify the configuration information represented by element  791 . Dialog box  700  comprises title bar  701 , command buttons  702 , 703 , execution environment information area  710 , resource adapter management area  720 , and resource adapter-specific information area  730 . Title bar  701  displays the name of the type of resource adapter being configured. Command buttons  702  and  703  may be individually selected by the user using a keyboard or pointing device. Command button  702 , when selected, invokes processing to terminate the display of the dialog box. Any changes made by the user to information displayed in the dialog box are saved during such termination processing. Command button  703 , when selected, also invokes processing to terminate the display of the dialog box, but without saving any changes made by the user. 
     Dialog box area  710  displays information about the execution environment of the target data source. Such information may include, for example, whether the data source resides on the same or different computer as the resource adapter software, or information about the coding methods used to represent data on the computer where the target data source executes. 
     Dialog box area  720  displays information principally used by the PAD software to manage any process executing a resource adapter using the instant configuration. The “Resource Type” field indicates the kind of data source to which the resource adapter connects. The “Resource Name” field indicates a name to be used by other software components to identify the resource adapter. The “Config File Name” field indicates the name of a resource adapter file in the configuration database where the instant configuration information is stored. The “Host Name” field indicates the name by which the data source computer can be contacted by software components attached to a common communication system. The “Instances” field indicates the number of concurrent resource adapters that may execute using the instant configuration information. The “Command” field indicates a command that the PAD may send to the operating system to initiate the resource adapter process. The “Restart Command” field indicates a command that the PAD may send to the operating system to attempt a restart of the resource adapter process after an earlier failure. The “Retries(number, sec)” fields indicate the number of times the PAD issues the restart command if the previous start or restart command fails within the specified number of seconds. The “Wait” field indicates the amount of time that PAD should wait after issuing a start or restart command to determine whether the command was successful. The “Restart” field indicates whether PAD should issue a restart command after detection of an earlier start or restart failure. The “Environment” field indicates information that the operating system should make available to the executing resource adapter software should it make a request for such information using operating system services. 
     The information displayed in area  720  of resource dialog box  700  is common to all types of resource adapters. Particular types of resource adapters may require that specific additional information be included in their configuration files. Display area  730  of resource dialog box  700  accommodates such information. For example, the “CICS Region” field indicates the name of a particular execution copy of CICS-EPI software running on the target data source computer. 
       FIGS. 8 through 10  illustrate the configuration of SS transactions between a DOM server and a CICS-EPI data source.  FIG. 8  illustrates the configuration of an SS transaction for a CICS-EPI data source. When element  791  for the EPI data source is added to the resource display area at the specific request of the user, “Transactions” element  891  is automatically available for display. “Transactions” element  891  serves as the anchor point for a list of server-source (SS) transactions that the EPI resource adapter can process. The user of the DOM Configurator specifically adds the “GetCustomer” display element  892  to the transactions list anchored by element  891 . When GetCustomer  892  is added to the transactions list, “EPI Script” element is automatically anchored off of GetCustomer element  892 , because configuration information represented by the “EPI Script” element  893  is necessary to conduct an SS transaction with a CICS-EPI-type data source. 
     Dialog box  810  illustrates the configuration information immediately represented by GetCustomer element  892 . A “Name” field indicates a transaction name by which the CS transaction is known within the configuration database. The transaction name must be unique within the resource adapter configuration to which it belongs. 
     Dialog box  820  illustrates the configuration information represented by “EPI Script” element  893 . A script field contains procedural logic necessary to carry out the SS transaction. The procedural statements in the script emulate the actions of a computer terminal operator to the data source when executed. Such actions may include, for example, reading an item off the screen, entering an item using a keyboard, or depressing control keys on the keyboard. Data items read from, or keyed to, the emulated terminal screen go to, or come from, named variables or literal string. Named variables may reside within data container objects in the DOM core. 
     To start the CICS transaction suggested by the example script of dialog box  820 , a terminal user would send a message to the EPI data source containing the transaction code to identify the desired transaction, “CINQ,” followed by an ATM card number to identify the particular customer for which the transaction is being requested. The first line of the script in dialog box  820  duplicates this message format using a literal value for the transaction code (“CINQ”), and variable substitution for the ATM card information (“$atmCardCode”). After receiving such a message, the EPI data source responds with a data stream to produce screen image  800  for the terminal user to read. Screen image  800  corresponds to persistent data record  172  of  FIG. 1 . The EPI script in dialog box  820  “reads” the screen image data stream using the second and subsequent lines of the script. The second line reads field  881 , and places the data item in a variable named output.id. Similarly the third and fourth lines read fields  882  and  883 , and place the data items in variables named output.name and output.branch, respectively. Table 1 portrays EPI scripting language elements useful to emulate terminal operations. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 EPI Scripting Language Elements 
               
            
           
           
               
               
            
               
                 Language 
                   
               
               
                 Element 
                 Description 
               
               
                   
               
               
                 Start ( ) 
                 This function starts the given transaction using the 
               
               
                   
                 specified parameter string. 
               
               
                   
                 Start (Transaction Name, Parameter String); 
               
               
                 Send ( ) 
                 This Function simulates attention keys by sending data 
               
               
                   
                 from the setField ( ) function to the transaction. 
               
               
                   
                 Attention key values are: 
               
               
                   
                 PF1-PF24 
               
               
                   
                 ENTER 
               
               
                   
                 CLEAR 
               
               
                   
                 Send (Attention Key); 
               
               
                 Clear ( ) 
                 This function clears the screen. 
               
               
                   
                 Clear ( ); 
               
               
                 ClearUnprot ( ) 
                 This function clears all unprotected fields on the 
               
               
                   
                 screen. 
               
               
                   
                 ClearUnprot ( ); 
               
               
                 SetCursor ( ) 
                 This function positions the cursor on the screen using 
               
               
                   
                 row/column coordinates. 
               
               
                   
                 setCursor (Row, Column); 
               
               
                 Keyboard ( ) 
                 This method takes a string of keystroke characters, and 
               
               
                   
                 updates the screen buffer as if someone typed the 
               
               
                   
                 characters on a keyboard. The function doesn&#39;t 
               
               
                   
                 support attention keys. The method also accepts 
               
               
                   
                 certain three character escape sequence keys. 
               
               
                   
                 Keyboard (Input String); 
               
               
                 Home ( ) 
                 This function positions the cursor at the 0,0 screen 
               
               
                   
                 coordinates. 
               
               
                   
                 home ( ); 
               
               
                 SetField ( ) 
                 This function sets the screen field value. There are 
               
               
                   
                 three values: FieldValue is a string that contains the 
               
               
                   
                 field value; Row is the row coordinate of the field to 
               
               
                   
                 set; and Column is the column coordinate of the field 
               
               
                   
                 to set. 
               
               
                   
                 setField (FieldValue, Row, Column); 
               
               
                 GetField ( ) 
                 This function returns the screen&#39;s field value as a 
               
               
                   
                 string. The function takes two values: first, Row is the 
               
               
                   
                 row coordinate of the field to set; and second, Column 
               
               
                   
                 is the column coordinate of the field to set. 
               
               
                   
                 FieldValue = GetField (Row, Column); 
               
               
                 FindField ( ) 
                 This function finds the first field on the screen 
               
               
                   
                 containing a regular expression. There are three 
               
               
                   
                 values: Expression is a string that contains the 
               
               
                   
                 expression value; Row is the row coordinate of the 
               
               
                   
                 found field; and Column is the column coordinate of 
               
               
                   
                 the found field. 
               
               
                   
                 FindField (Expression, Row, Column); 
               
               
                 &amp;FM 
                 Field Mark 
               
               
                 &amp;HO 
                 Home 
               
               
                 &amp;Ln 
                 Cursor Left n Times 
               
               
                 &amp;Nn 
                 Newline n Times 
               
               
                 &amp;Rn 
                 Cursor Right n Times 
               
               
                 &amp;Tn 
                 Tab n Times 
               
               
                 &amp;Un 
                 Cursor Up n Times 
               
               
                 &amp;Bn 
                 Back Tab n Times 
               
               
                 &amp;Dn 
                 Cursor Down n Times 
               
               
                 &amp;DL 
                 Delete 
               
               
                 &amp;DU 
                 Dup 
               
               
                 &amp;EF 
                 Erase to End-of-field 
               
               
                   
               
            
           
         
       
     
       FIGS. 9 and 10  illustrate the configuration of GetSavings and GetBankcard EPI SS transactions, respectively, in parallel fashion to the configuration of the GetCustomer transaction illustrated and just described in relation to  FIG. 8 . Screen image  900  of  FIG. 9 , and screen image  1000  of  FIG. 10 , correspond to persistent data records  176  and  178  of  FIG. 1 , respectively. 
       FIG. 11  illustrates the configuration of a relational database management software system (RDBMS) used as a data source. The configuration of the RDBMS data source parallels the configuration of the EPI data source illustrated and described in relation to  FIG. 7 . The “Informix (RDBMS)” element  1191  of the visible contents  664  from the resource display area ( 660  of  FIG. 6 ) of the DOM Configurator main screen ( 600  in  FIG. 6 ) represents the configuration information for an RDBMS data source  130   e . Dialog box  1100  comprises execution environment information area  1110 , resource adapter management area  1120 , and resource adapter-specific information area  1130 . 
     Dialog box area  1110  displays information about the execution environment of the target data source. The types of information contained in display area  1110  are the same as for display area  710  described earlier in reference to  FIG. 7 . Dialog box area  1120  displays information principally used by the PAD software to manage any process executing a resource adapter using the instant configuration. The types of information contained in display area  1120  are the same as for display area  720  described earlier in reference to  FIG. 7 . Display area  1130  contains no information, as no additional information beyond that accommodated in display areas  1110  and  1120  is needed to manage the execution of an RDBMS-type resource adapter 
       FIG. 12  illustrates the configuration of a session definition as may be required by RDBMS software. When display element  1191  for the Informix RDBMS data source is added to the resource display area at the specific request of the user, “Sessions” element  1192  is automatically available for display. “Sessions” element  1192  serves as the anchor point for a list of logical sessions the resource adapter may establish with the data source in order to interact with the data source. The user of the DOM Configurator specifically adds the “sys2_informix_session” display element  1291  to the sessions list anchored by element  1192 . Each session element, such as  1291 , represents configuration information for a logical connection to the RDBMS data source. 
     Dialog box  1200  displays the configuration information underlying session element  1291 . The “Session Name” field indicates an identifier by which the instantly configured session may be known. The “Database Type” field indicates the name of a library file containing program code that can transform SS transaction requests and responses between a generalized RDBMS format and a format required by a particular RDBMS data source. The “Database Type” field is used because the design of this embodiment employs a generalized RDBMS resource adapter that is specialized to a particular RDBMS server by this association to a related library file. The “Server Name” field indicates the name by which the data source computer can be contacted by software components attached to a common communication system. The “Database Name” field indicates the name by which the RDBMS server identifies the particular database containing the data items targeted for access. The “Database Role” field indicates the function of connection; e.g., whether the connection is used to connect a client for data access requests, or whether the connection is used for performing data base administration activities. The “User ID” and “Password” fields indicate security parameters that will authenticate and authorize the resource adapter to utilize the services of the RDBMS data source. The “# of Connections” field indicates the number of logical connections the resource adapter should establish between itself and the data source using the instant configuration information. The “# of Output Rows” field indicates the default maximum number of table rows that should be included in the response to an SS transaction request originating from the resource adapter. 
     Notably, no sessions list is included in the configuration information for a CICS-EPI data source already described in relation to  FIG. 7 . This is because different data sources impose different interface requirements. In a preferred embodiment, the construction of the DOM configurator software is similar to that of the DOM server software wherein the resource adapters interface to the DOM core in a common fashion to provide a degree of modularity. In a preferred embodiment, resource adapter configuration maintenance code, including the program code to effectuate the dialog boxes related to the particular resource adapter, are modular in design and interface to “core” GUI-based DOM Configurator code using a common interface. Such a construction improves the upgradability of the DOM Configurator as new types of data sources become desired. 
       FIG. 13  illustrates the configuration of an SS transaction between a DOM server and an RDBMS data source. In concept, this parallels the configuration of an SS transaction between a DOM server and a CICS-EPI data source—the transaction configuration contains all of the information necessary to conduct a transaction. In detail, however, the configuration information and its organization differ for an RDBMS transaction. 
     When display element  1191  for the Informix RDBMS data source is added to the resource display area at the specific request of the user, “Transactions” element  1193  is automatically available for display. “Transactions” element  1193  serves as the anchor point for a list of server-source (SS) transactions that the Informix RDBMS resource adapter can process. The user of the DOM Configurator specifically adds the “GetSecurity” display element  1391  to the transactions list anchored by graphical element  1193 . When GetSecurity  1391  is added to the transactions list, “Parameters”  1392 , “Field Map”  1393 , and “SQL”  1395  elements are automatically anchored off of GetSecurity element  1391 . Parameter  1392  and SQL  1393  configuration elements each directly possess underlying configuration-information. Field map element  1393  serves as the anchor point for a list. Each entry in the field map list establishes the correspondence between a data item in a DOM data container object and a data item accessed using the RDBMS. 
     Dialog box  1310  illustrates the configuration information immediately represented by GetSecurity element  1391 . A “Name” field indicates a transaction name by which the CS transaction is known within the configuration database. The transaction name must be unique within the resource adapter configuration to which it belongs. 
     Dialog box  1320  illustrates the configuration information represented by “Parameters” element  1392 . A “Type” field indicates whether the database processing for the transaction is defined by structured query language (SQL) statements supplied to the data source by the resource adapter or by a predefined procedure stored on the data source computer. If a predefined procedure is to be used, the name of the procedure must be indicated in the “Proc Name” field. If SQL statements are to be supplied to the data source by the resource adapter, the SQL statements are specified using dialog box  1340 . SQL statements specified using dialog box  1340  may include substitution variables such as the “$id” variable shown in dialog box  1340 . SQL and variable substitution techniques are well known and understood in the art. A “Session Name” field in dialog box  1320  indicates the name of database session to utilize in conducting the transaction. Such a session must have already been configured in accordance with the discussion regarding  FIG. 12 . A “# of Output Rows” field indicates the maximum number of table rows that should be included in the response to the instant SS transaction request. This number overrides the default specified in the session configuration as discussed previously in reference to  FIG. 12 . 
     Dialog box  1330  illustrates the configuration information represented by “password” element  1394 . Password element  1394  belongs to the field map list. Field map list items direct the automatic transfer of data items between data container objects in the DOM server and data fields managed by the RDBMS data source. The user of the DOM Configurator specifically adds the “password” display element  1394  to the field map list anchored by field map element  1393 . An “Attribute Name” field indicates the name of a particular data item stored in a data container object within the DOM server. The data container determines the direction of the data item transfer. If the relevant data container object relates to a request message from a client to the DOM server, the data item moves from the data container object to the data source field before the SS transaction request is sent to the data source. If the relevant data container object relates to a response message to be sent from the DOM server to the client, the data item moves from the data source field to the data container object after the SS transaction response is received from the data source. The same attribute name may be configured into both the request-related and response-related data containers configured for a CS transaction. Configuration of request and response data containers is discussed later in reference to  FIG. 14 . A “Field Name” field in dialog box  1330  indicates the name used by the RDMBS data source to identify a particular data item field. 
     In this example, the “Field Name” of “Pass Phrase” is used to identify a data item from the second column of relational table  1300 . Row  1301  of relational table  1300 , corresponds to persistent data record  174  of  FIG. 1 . In this example, the data item in the “Pass Phrase” column comes from Row  1301  of relational table  1300 . 
     Method (CS Transaction) Configuration 
     After resources have been configured (i.e., SS Transactions), methods that use them can be configured (i.e., CS transactions). The configuration activity represented by  FIGS. 14 and 15  correspond to the activity represented by step  540  of  FIG. 5 . 
       FIGS. 14 through 15  illustrate the configuration of a CS transaction between a client application program and a DOM server. Referring first to  FIG. 14 , the “GetCustomerInfo” element  1492  of the visible contents  652  from the method display area ( 650  of  FIG. 6 ) of the DOM Configurator main screen ( 600  in  FIG. 6 ) represents the configuration information for a CS transaction that may be requested by application program  220 . After adding element  1492  to the method display area, the user of the DOM Configurator may display a dialog box  1410  to view and modify the configuration information represented by the element  1492 . A “Name” field in dialog box  1410  indicates a name to uniquely identify the transaction among those in the list anchored by graphical element  1491 . This name will be used by application program  220  to request the transaction from the DOM server. 
     When element  1492  for the GetCustomerInfo CS transaction is added to the methods display area at the specific request of the user, “Input Message” element  1493 , “Output Message” graphical element  1494 , “Transactions” graphical element  1495 , and “Script” graphical element  1496  are automatically available for display. “Input Message”  1493  and “Output Message”  1494  elements represent the request and response messages, respectively, exchanged between the client and the DOM server. “Transactions”  1495  and “Script”  1496  elements represent the processing performed by the DOM server to satisfy the client&#39;s request. In the presently described embodiment, either the Transactions  1495  element or the Script  1496  element will determine the processing for the transaction, and only one of the two may be further configured. “Input Message”  1493  and “Output Message”  1494  elements each serve as the anchor for a potentially multi-level, hierarchical list of message node elements. The hierarchical arrangement of the message node lists reflects the hierarchical arrangement of data container objects that DOM server software constructs at run-time to embody the input and output messages, as well as the hierarchical arrangement of programming objects in application program  220 . 
     The user of the DOM Configurator specifically adds the “atmCardCode” message node element  1497  to the Input Message list anchored by element  1493 . The atmCardCode element represents the sole data item passed from a client to the DOM server when requesting a GetCustomerInfo transaction. The atmCardCode data item is then used as a search argument by the DOM server when preparing a request for SS transaction GetCustomer to fulfill the client&#39;s GetCustomerInfo request (discussed in reference to  FIG. 8 ). Dialog box  1420  illustrates the configuration information immediately represented by atmCardCode element  1497 . A “Name” field indicates a name to uniquely identify the node within parent message element  1493 . The “Type” field indicates the role of the message node within the hierarchical list. A component-type message node corresponds to a data item to be transferred between the client application program and the DOM server. The “Option” field is used when dialog box  1420  is used to insert a new message node. The “Option” field indicates the position in the hierarchical list for the node to occupy, relative to the most recently selected element. Here, the most recently selected element is  1493 . “Next” and “Previous” indicate that the new node should occupy the subsequent or preceding position, respectively, at the same level in the hierarchy. “Child” indicates that the new node should occupy a related position, one level lower in the hierarchy. The “Index” field is described later in relation to message mode  1593 . The “Index” field is meaningful only for component-type message nodes. 
     While the input message configured under anchor element  1493  contains only one element  1497 , the output message for the GetCustomerInfo CS transaction configured under element  1494  contains multiple elements arranged in a two-level hierarchy. The hierarchy corresponds to the programming object hierarchy illustrated in  FIG. 1 . The upper level of the object hierarchy includes an object  160  to represent a banking customer. The lower level of the object hierarchy includes multiple objects  162 - 164 , each of which represents a particular account owned by the banking customer. In the output message configuration depicted in  FIG. 14 , the upper level of the hierarchy begins at Customer element  1498 , and the lower level of the hierarchy begins at Account element  1499 . 
     The user of the DOM Configurator specifically adds the “Customer” message node element  1498  to the Output Message list anchored by element  1494 . Dialog box  1430  illustrates the configuration information immediately represented by Customer element  1498 . The fields and their meanings are the same for all message nodes as described above in relation to dialog box  1420 . The “Type” field in dialog box  1430 , however, indicates the role of this message node to be of type “Folder.” A folder-type message node indicates within a message that the object in the application program  220  that embodies data items represented by immediately subordinate nodes, is instantiated from a class type that is dynamically determined at run-time. The customer folder node represents the finite family of class types from which the object may be instantiated. Notably, the customer folder “represents” the family of class types without having any awareness of what the members of the family are. That information is created by the application programmer and is ensconced within the application program  220  itself. The list of component message nodes immediately subordinate to the folder node represents the set of all field types that can potentially be exchanged during the servicing of a particular instance of a GetCustomerInfo transaction. The list of field types actually exchanged for a particular instance of the GetCustomerInfo transaction will correspond to the class-type family member used to instantiate the related programming object in the client application program  220 . 
     In reference to  FIG. 15 , the user of the DOM Configurator specifically adds the immediately subordinate “id” message node element  1591  to the Customer folder node  1498 . Dialog box  1510  illustrates the configuration information represented by “id” element  1591 . The “name,” “branch,” and “password” elements exist under the Customer folder node in like fashion. 
     The user of the DOM Configurator specifically adds the Account folder node  1499  under Customer folder node  1498 . The configuration information represented by Account folder graphical element  1499  parallels that for Customer folder node  1498  as displayed by dialog box  1430  (see  FIG. 14 ), with the obvious change to the contents of the “Node Name” field. 
     The user of the DOM Configurator specifically adds the Account array message node  1592  under Account folder node  1499 . The configuration information represented by Account array element  1592  is displayed by dialog box  1520 . The noteworthy difference between the configuration information for the account array message node  1592 , and the configuration information for the message nodes previously described, is the selection of “Array” for the contents of “Type” field  1524 . An array-type message node indicates within a message that multiple occurrences of the set of message nodes subordinate to the array-type message node may be contained within a single message occurrence. In the presently described example, account array node  1592  provides for the GetCustomerInfo response message to contain data regarding multiple accounts. 
     The user of the DOM Configurator specifically adds the “number” message node  1593  under Account array node  1592 . The configuration information represented by “number” element  1593  is displayed by dialog box  1530 . The noteworthy difference between the configuration information for the “number” component-type message node  1593 , and the configuration information for the component-type message nodes previously described, is the affirmative entry for the contents of “Index” field  1538 . The affirmative entry for the contents of “Index” field  1538  indicates that the data item represented by the “number” component node can serve to uniquely identify one set of account array subordinate nodes from among the multiple sets that may exist by virtue of array node  1592 . Component-type nodes “type,” “status,” “balance,” and “creditLimit” are configured as other component-type nodes. If any of these nodes is also configured with an affirmative indication in its “Index” field, then it is combined with the “number” node to form the unique identifier for the set of array subordinate nodes. 
     “Transactions”  1495  and “Script”  1496  elements represent the processing performed by the DOM server to satisfy the client&#39;s request. As mentioned earlier, in the presently described embodiment, either the Transactions  1495  element or the Script  1496  element will determine the processing for the transaction, and only one of the two may be further configured. In the present example, Transactions element  1495  is further configured to represent the data source processing for the GetCustomerInfo CS transaction. Transactions element  1495  serves as an anchor for an ordered list of SS transactions. In the present example, the “EPI.GetCustomer,” “Informix.GetSecurity,” “EPI.GetSavings,” and “EPI.GetBankcard” elements were actively placed under Transactions element  1495  by the user of the DOM Configurator. This action may have been performed in a preferred embodiment by using a drag-and-drop user interface technique, well known in the art, to “copy” an SS transaction element, such as GetCustomer, from the resource display area ( 660  of  FIG. 6 ) to Transactions element  1495 . When copied, the SS transaction is identified by the concatenation of the resource element name under which the SS transaction element is configured, a period (“.”), and the SS transaction element name. When the DOM Server performs a CS transaction using a Transactions list, the SS transactions are performed sequentially, in the order they appear in the list. Other embodiments may permit non-sequential, and/or out-of-order processing of the transactions in the list by providing automatic or user-specified mechanisms to mandate ordered processing between transactions having an interdependency. An example of such an interdependency is hypothetical transaction B, the request message for which includes data originating from hypothetical transaction A. 
     Alternatively, DOM server processing for a CS transaction can be directed by the configuration information of a “Script” graphical element such as element  1496 . In this case, a dialog box like the dialog box used to maintain SQL statements ( 1340  of  FIG. 13 ) or the dialog box used to maintain CICS-EPI scripts ( 820  of  FIG. 8 ) is used to maintain the script configuration information represented by Script element  1496 . In a preferred embodiment the scripting language is DOM-specific, but modeled closely after a widely known programming language such as C. The scripting language may include support for a variety of data types, variable manipulation, arithmetic and logical operators, program flow control statements and structures, string-related functions, and specialty functions useful in navigating and manipulating hierarchical lists and object structures. Elements of an exemplary scripting language appear in Table 2. The scripting language of a preferred embodiment also provides the capability to execute configured SS transactions. Such a scripting language extends the capability of the DOM server to provide advanced functionality, e.g., as conditional error handling or user-implemented commit and rollback processing across disparate data sources. The extended capability provided by the scripting language represents a further advantage of the present invention. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 General Scripting Language Elements 
               
            
           
           
               
               
            
               
                 Element 
                 Description 
               
               
                   
               
            
           
           
               
            
               
                 Data Types 
               
            
           
           
               
               
            
               
                 long, double, string, 
                 enjoy sstandard usage as in other computer 
               
               
                 boolean 
                 languages like C 
               
               
                 pointer 
                 to introduce hidden variables, i.e., variables that 
               
               
                   
                 belong to another context, e.g., a different CS 
               
               
                   
                 transaction processing request. 
               
               
                 identifier 
                 represents a name of a variable. A &#39; character 
               
               
                   
                 (i.e., on the apostrophe key) represents an 
               
               
                   
                 identifier in an argument. 
               
               
                 user-defined 
                 The user-defined type allows you to manipulate 
               
               
                   
                 user-defined objects within a script. 
               
               
                   
                 User-defined data types use qualified names 
               
               
                   
                 having a dot notation (e.g., parent.child). 
               
            
           
           
               
            
               
                 Variable Manipulation 
               
            
           
           
               
               
            
               
                 = 
                 assignment operator 
               
            
           
           
               
            
               
                 Operators 
               
            
           
           
               
               
            
               
                 + − * / − 
                 addition, subtraction, multiplication, division, 
               
               
                   
                 unary; standard arithmetic 
               
               
                 &amp;&amp; ∥ ! 
                 AND, OR, NOT; standard logic 
               
               
                 &lt; &gt; &lt;= &gt;= != 
                 less than, greater than, less or equal, greater or 
               
               
                   
                 equal, not equal; standard comparison 
               
            
           
           
               
            
               
                 Program Flow 
               
            
           
           
               
               
            
               
                 if...then 
                 conditional branch 
               
               
                 while...endloop 
                 top-checking loop 
               
               
                 do...until 
                 bottom-checking loop 
               
               
                 continue, break, goto, 
                 standard use 
               
               
                 exit 
               
            
           
           
               
            
               
                 String Functions 
               
            
           
           
               
               
            
               
                 string( ) 
                 converts any native type variable (e.g., long, 
               
               
                   
                 double, etc.) to a string. 
               
               
                 substring( ) 
                 creates a substring from another string. 
               
               
                   
                 format: substring(source, start, length) 
               
               
                 index( ) 
                 searches for the first occurrence of a substring 
               
               
                   
                 within a string. 
               
               
                 length( ) 
                 returns the length of the specified string. 
               
            
           
           
               
            
               
                 Hierarchy Functions 
               
            
           
           
               
               
            
               
                 child_count( ) 
                 returns the number of children for the element 
               
               
                 child( ) 
                 returns a tree that corresponds to one of the 
               
               
                   
                 tree&#39;s child nodes or a NULL tree if the node 
               
               
                   
                 doesn&#39;t exist; otherwise, it returns a native-value 
               
               
                   
                 defined by a leaf type. 
               
               
                 clone( ) 
                 creates a cloned copy of the FDO tree or its 
               
               
                   
                 subtree specified by the path. 
               
               
                 connect( ) 
                 connects an FDOTree to a user-object 
               
               
                   
                 identifier or a passed-in argument in the 
               
               
                   
                 specified path. This function behaves like the 
               
               
                   
                 assignment operator with user-objects; 
               
               
                 name( ) 
                 returns an element name (a string) corresponding 
               
               
                   
                 to the tree-element residing under the specified 
               
               
                   
                 path. 
               
               
                 disconnect( ) 
                 disconnects a node from the specified path. 
               
               
                 destroy( ) 
                 destroys a subtree specified by an identifier and 
               
               
                   
                 path. 
               
               
                 element_type( ) 
                 this function returns a code corresponding to its 
               
               
                   
                 type, i.e., non-existent, long, double, string, or 
               
               
                   
                 node. 
               
               
                 make_node( ) 
                 creates an empty node specified by the identifier 
               
               
                   
                 and an optional path. 
               
            
           
           
               
            
               
                 Miscellaneous 
               
            
           
           
               
               
            
               
                 print 
                 print the value of variables to an output file or 
               
               
                   
                 device 
               
               
                 exist( ) 
                 returns true if a variable with the specified name 
               
               
                   
                 exists in the context space; otherwise, it returns 
               
               
                   
                 false. 
               
               
                 execute( ) 
                 performs the named SS transaction 
               
               
                   
               
            
           
         
       
     
       FIG. 16  illustrates a screen display for viewing configuration data in text format. The GUI-based Configurator provides the screen display depicted by window  1600  as an aid in troubleshooting and understanding. Window  1600  comprises “Resources” area  1610 , “Resource Configuration” area  1620 , and “DOM Configuration” area  1630 . Resources area  1610  displays a list of the names of configured resources, i.e., data sources. The presently selected resource name appears as light text against a dark background. “Resource Configuration” area  1620  displays the configuration for the presently selected resource of area  1610  in text format. In the sample text depicted in display area  1620 , “Method” refers to “SS transaction.” The contents of display area  1620  corresponds to the contents of a Resource Adapter configuration file  576  as depicted in  FIG. 5 . 
     “DOM Configuration” area  1630  displays configuration information in text format. In the sample text depicted in display area  1630 , “Simplemethod” refers to a CS transaction, and “Submethod” refers to an SS transaction. The contents of display area  1630  corresponds to the contents of a DOM configuration file  574  as depicted in  FIG. 5 . 
     It is noted that other GUI-configurator screen displays similar to those depicted in  FIGS. 6 through 16  may be implemented to provide viewing and/or editing of any information in the configuration database. For example, GUI-configurator screens maybe be implemented for the PAD configure. One skilled in the art recognizes that various screen formats and organizations may be used without departing. After the implementation process depicted and described in relation to  FIG. 5  is complete, execution of an embodiment employing the present invention can begin. 
     The Execution Process 
       FIG. 17  is a flowchart showing the execution process for one system. Step  1702  initializes the data sources. Data sources may run on one or more host computers. For each data source, the software program code for the data source is loaded into computer memory from mass storage media  1730 , such as a hard disk. The loading operation is performed by the operating system on the data source host computer. Once loaded into memory, the operating system passes control of the computer to the program code of the data source software. The program code then prepares the data source host computer to receive and process SS transaction requests. 
     Step  1704  initializes the DOM server. The DOM server may run on a host computer shared with one or more data sources, or it may run on a separate machine. The software program code for the DOM server is loaded into computer memory from mass storage media  1730 , such as a hard disk. The loading operation is performed by the operating system on the DOM server host computer. Once loaded into memory, the operating system passes control of the computer to the program code of the DOM server software. The program code then prepares the DOM server host computer to receive and process CS transaction requests. The DOM server software uses information from the configuration database  115  to direct the initialization process. As part of initialization, The DOM server software may establish communication with one or more data sources started in step  1702  in anticipation of sending SS transaction requests to the data sources in order to process the CS transaction requests the DOM server software receives. 
     Step  1706  initializes the user application program. The user application program may run on a computer shared with one or more data sources, on a computer shared with the DOM server, or it may run on a separate machine. The software program code for the application program  242  is loaded into computer memory from mass storage media  1730 , such as a hard disk. The loading operation is performed by the operating system on the application program host computer. Once loaded into memory, the operating system passes control of the computer to the program code of the application program. The program code then performs the data processing operations desired by the user. In the course of these data processing operations the client application program makes a CS transaction request. 
     The running application program makes a request to the DOM server in step  1708  to perform a CS transaction. In making the request, the application program communicates information to the DOM server. Such information may include, for example, the type of CS transaction to perform and identifiers for the specific data items to be accessed. 
     In step  1710 , the DOM server determines the SS transactions needed to fulfill the request made by the application program in step  1708 . The DOM server identifies the transactions using information loaded from configuration database  115 . The identities of the SS transactions come from either the transactions list or the script configured for the method (the CS transaction) as recorded in the configuration database  115  and discussed earlier in reference to  FIG. 15 . 
     In step  1712 , the DOM server requests performance of an SS transaction identified in step  1710 , using information loaded from configuration database  115 . In making the SS transaction request, the DOM server communicates relevant information to the appropriate data source. Such information may include, for example, the type of SS transaction to perform and identifiers for the specific data items to be accessed. Some of the information communicated to the data source by the DOM server, may have originally been communicated to the DOM server by the client application program. For example, the application program may communicate a customer number to the DOM server, which in turn communicates the customer number to the data source. The data source, in turn, accesses specific data items contained among its stored data  432  that are associated with that customer number. 
     In step  1714 , a data source receives the SS transaction request communicated by the DOM server in step  1712 . The data source processes the request, accessing relevant data items contained among stored data  432 . The data source concludes the SS transaction by indicating the results of the processing in a response information message that is communicated to the DOM server. 
     After receiving the response information communicated from the data source in step  1714 , the DOM server determines whether any SS transactions identified in step  1710  have yet to be performed. If transactions remain, the DOM server returns to step  1712  to process the next SS transaction. If the needed SS transactions are completed, the DOM server resumes operation with step  1718 . 
     In step  1718 , the DOM server completes the processing for the CS transaction using information loaded from configuration database  115 . The DOM server determines the format of the response message based on the type of CS transaction. The DOM server then constructs a response message in the required format, using data items received and consolidated from possibly multiple SS transactions. The constructed response message is then communicated to the client application program. 
     In step  1720 , the application program receives the formatted response to its CS transaction request, as communicated by the DOM server in step  1718 . Data items represented in the response message are extracted from the message. Program code in the application program embodies the extracted data items into programming objects. The programming objects are interrelated into a topology which is, itself, also represented in the response message. After the programming objects embody the data items from the response message, the application program continues execution in step  1722 . Downstream instructions in the application program may then utilize the programming objects of step  1720  to usefully employ the data items the objects embody. In accordance with the present invention, the programming object data items reflect persistent copies of corresponding data items contained in stored data  432  and maintained by the data access software. 
       FIG. 18  depicts one construction of a data stream for communication between a client application program and a DOM server during the execution process discussed in reference to  FIG. 17 . The data stream of  FIG. 18  is constructed of tokens. Each token comprises a token length indicator followed immediately by token data. Token instances  1892 ,  1894 , and  1895  depict examples of each of the three possible token coding formats. The difference between the formats lies in the coding of the length indicator portion of the token. The first character of the token determines the coding format of a particular token. The meanings ascribed the first token character appear in Table 3. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Token Formats 
               
            
           
           
               
               
               
            
               
                 Format 
                 First 
                   
               
               
                 Group 
                 Character 
                 Subsequent Characters (Bytes) 
               
               
                   
               
               
                 I 
                 0 
                 none: empty value 
               
               
                   
                 1 
                 the token data is contained in 1 byte 
               
               
                   
                 2 
                 the token data is contained in 2 bytes 
               
               
                   
                 3 
                 the token data is contained in 3 bytes 
               
               
                   
                 4 
                 the token data is contained in 4 bytes 
               
               
                 II 
                 5 
                 the length of the value is represented in the 
               
               
                   
                   
                 next 1 byte and token data immediately 
               
               
                   
                   
                 follows 
               
               
                   
                 6 
                 the length of the value is represented in the 
               
               
                   
                   
                 next 2 bytes and token data immediately 
               
               
                   
                   
                 follows 
               
               
                   
                 7 
                 the length of the value is represented in the 
               
               
                   
                   
                 next 3 bytes and token data immediately 
               
               
                   
                   
                 follows 
               
               
                   
                 8 
                 the length of the value is represented in the 
               
               
                   
                   
                 next 4 bytes and token data immediately 
               
               
                   
                   
                 follows 
               
               
                   
                 9 
                 the length of the value is represented in the 
               
               
                   
                   
                 next 5 bytes and token data immediately 
               
               
                   
                   
                 follows 
               
               
                 III 
                 Any Other 
                 none: the length of the token data is 
               
               
                   
                   
                 implicitly 1 byte and the first character is the 
               
               
                   
                   
                 token data 
               
               
                   
               
            
           
         
       
     
     For format group I tokens, the first character may be 0 through 4 and represents the number of bytes of token data to immediately follow. A first character of ‘0’ indicates that zero bytes follow and thus may be used to represent an empty value. Token instance  1895  depicts an example of a format group I token. The first character is a ‘2’ indicating that two bytes of token data follow, those being the characters “RW.” For format group II tokens, the first character may be 5 through 9 and represents a number of characters to follow that, themselves, contain a representation for the number of bytes of token data to follow immediately thereafter. Token instance  1892  depicts an example of a format group II token. The first character is a ‘6’ indicating that two bytes representing the length of token data follow. The next two characters are “11” indicating that eleven bytes of token data follow, those being the characters “creditLimit.” For format group III tokens, the first character of the token is not the length of data, but rather is the data itself, having an implied length of one byte. Token instance  1894  depicts an example of a format group III token. The first character is a ‘C’ indicating that the character ‘C’ is the token data with an implied length of one byte. 
     Five different types of tokens may be used to construct a data stream. The various types of tokens differ according to their content. Some token types may be used to aggregate multiple tokens into a single token, thus encapsulating the multiple tokens. Such nesting by the tokenization process, producing tokens within other tokens, is advantageously employed to represent information in the data stream about the hierarchical topology that relates data items conveyed in the data stream. The hierarchical topology information logically segregates and distinguishes data items belonging to different levels of the hierarchy as well as those belonging to the same level. For example, a parent is segregated from its children at a lower level, and each child is segregated from the others on the same level. 
     The first type of token is the data stream token  1800  that contains the entire data stream. The data stream may correspond to either a request or a response message for exchange between a client and a DOM server. Data stream tokens correspond to the aggregation of all message nodes subordinated to an input message or output message element for a CS transaction (Method) configuration as discussed in relation to  FIGS. 14 and 15 . 
     The second type of token is the family token  1810  that occurs at the head of a branch in the topology of the hierarchy and specifies the object-type family to incorporate immediately following data items. Token  1850  is also a family-type token. Family tokens correspond to folder-type message nodes in the input or output message configuration for a CS transaction (Method) as discussed in relation to  FIGS. 14 and 15 , and may contain the name of the folder-type message node as the specifier for the object-type family. 
     The third type of token is the branch token  1820  that immediately follows a family token. A branch token contains all of the token information that logically depends from the preceding family token. Token  1850  is also a branch-type token. Branch tokens correspond to the aggregation of all message nodes subordinated to a folder-type message node in an input or output message configuration for CS transaction (Method) as discussed in relation to  FIGS. 14 and 15 . 
     The fourth type of token is the business object token  1840 . A business object token corresponds to an instance of an object having an object-type, i.e., class, belonging to the family represented by its immediately preceding family token. Tokens  1860  and  1870  are also business object tokens. The business object token aggregates data items to be embodied by an object instance. A business object token further corresponds to some subset or the full set of component-type message nodes directly subordinated to the same message node in an input or output message configuration for a CS transaction (Method) as discussed in relation to  FIGS. 14 and 15 . For example, a business object token populated by the DOM core using data obtained from a GetSavings SS transaction will aggregate tokens corresponding to number, type, status, and balance component message nodes directly subordinated to Account array node  1592  of  FIG. 15 . It will not include a token corresponding to the creditLimit component message node similarly subordinated. This is because the CICS-EPI SINQ display screen ( 900  of  FIG. 9 ) underlying the GetSavings CS transaction does not provide a creditLimit data item. 
     The fifth type of token is the leaf token  1871 . A leaf token corresponds to one particular component-type message node in an input or output message configuration for a CS transaction (Method) as discussed in relation to  FIGS. 14 and 15 . Token  1871  is the only leaf token depicted in  FIG. 18 , although a multiplicity of such embedded tokens are implied by the dashed-line portions depicting business object tokens  1840 ,  1860 , and  1870 . Token  1871  comprises tokens  1871 - 1877 . The “data item” itself is contained by token  1876 , the “value” token. The remaining tokens contained by leaf token  1871  contain information about the data item, i.e., they contain metadata. “Field type” token  1872  specifies the role of the data item. For example, the data item may be the number “4445678” but the field type contents will instruct whether that is a phone number or an account number. “Data format” token  1873  specifies the storage and representation format of the data item, e.g., integer, floating point, or character string. “State” token  1874  specifies the state of the data item relative to the persistent storage copy to which it corresponds. For example, a state of “C” for “clean” indicates that the data item has not been changed. “Permission” token  1875  specifies the degree of control the client application may exercise over the persistent storage copy corresponding to the data item. For example, a permission of “RW” indicates that the client application program is registered via access control mechanisms to access the persistent storage copy for both read and write operations. The access control mechanisms may be implemented in one or more architectural layers occurring between the application program and the stored data, e.g., the data access layer. “Original value” token  1877  reflects the data item as it resided on persistent storage when first retrieved, i.e., its unchanged state. 
     Inclusion of metadata along with a data item facilitates data stream to object transformation, and permits sophisticated functionality to be included in the CS transaction processing performed by the DOM server. For example, a Method script on the DOM server could utilize the state, value, and original value data to implement commit/rollback processing for a CS transaction defined across multiple data sources. Using the same information, the commit/rollback script could minimize the SS update transactions performed to those that maintain data items that were actually changed by the application program. Inclusion of metadata along with a data item exchanged between a client and the DOM server represents a further advantage of the present invention. Inclusion of a scripting language facility in the DOM server that permits a user to configure the processing for a CS transaction using a procedural language, and that permits conditional processing based on data items and related metadata, represent further advantages of the present invention. 
       FIG. 19  is an object diagram of example programming objects used to relate and embody data items in a client application program. The objects depicted are instantiated in the client application program during the execution process, for example, in step  1720  of  FIG. 17 . Objects  160 ,  162 , and  164  of  FIG. 19  correspond to like numbered objects depicted in  FIG. 1 . These objects are primary application programming objects. Primary application programming objects may be used by an application programmer to each represent a real-world physical or conceptual business object about which related data is maintained by the data sources. In the example shown, the primary objects  160 ,  162 , and  164  represent a banking customer and the customer&#39;s savings and bankcard accounts, respectively. 
     Objects  1910 - 1916 ,  1930 - 1936 , and  1940 - 1948  have a correspondence to the transient data items shown within programming objects  160 ,  162 , and  164  in  FIG. 1  and discussed earlier in reference thereto. These objects are utility programming objects that support the work of primary application programming objects in representing a business object. Each of these objects belongs to a primary object and stores a particular data item and its metadata. Each object also provides an interface to the data item for other portions of the client application program. The interface further supports the exchange of the embodied data item and metadata with the DOM server. 
     Objects  1900  and  1920  have a correspondence to the Customer  1498  and Account  1592  folder-type message nodes, respectively, depicted and discussed in relation to  FIGS. 14 and 15 . These programming objects are also utility programming objects that support the work of primary application programming objects in representing a business object. Each of the folder utility objects facilitates the instantiation, population, organization, inventory, and exchange of primary application programming objects. Folder utility objects also participate in constructing a hierarchical topology by serving as a central point through which primary objects  162 , 164  belonging to the folder object  1920  are subordinated to the primary object  160  to which the folder object belongs. 
     The hierarchy of programming objects depicted in  FIG. 19  is such as may be constructed from the data stream depicted and discussed earlier in relation to  FIG. 18 . When the data stream of  FIG. 18  is, for example, transmitted from a DOM server to a client application program, a transmutation of the data stream components into programming objects, (objectization) occurs. The correspondence between data stream tokens and the programming objects extant after objectization is described next, followed by a procedural description of the objectization process in reference to  FIG. 20 . 
     Data stream token  1800  of  FIG. 18  corresponds to the entire collection of objects depicted in  FIG. 19 . Customer family-type token  1810  of  FIG. 18  corresponds to Customer folder utility object  1900  of  FIG. 19 . Customer branch-type token  1820  of  FIG. 18  corresponds to the entire collection of objects connected directly or indirectly via connection  1991  beneath Customer folder utility object  1900  of  FIG. 19 . Customer business object token  1840  of  FIG. 18  corresponds to Customer primary object  160  of  FIG. 19 . Account family token  1850  of  FIG. 18  corresponds to Account folder utility object  1920  of  FIG. 19 . Account branch-type token  1830  corresponds to the entire collection of objects connected directly or indirectly via connections  1993  and  1994  beneath Account folder utility object  1920  of  FIG. 19 . Account 1  business object token  1860  of  FIG. 18  corresponds to Savings Account primary object  162  of  FIG. 19 . Account 2  business object token  1870  of  FIG. 18  corresponds to Bankcard Account primary object  164  of  FIG. 19 . Representative leaf token  1871  of  FIG. 18  corresponds to data item utility object  1948  of  FIG. 19 . 
       FIG. 20  is an interaction diagram showing an example of the processing performed by a client application program to request and objectize data items. The illustrated steps show processing by an application program corresponding to steps  1708  and  1720  of the execution process described earlier in relation to  FIG. 17 . Specifically, step  2051  of  FIG. 20 , and steps  2053  through  2071  of  FIG. 20 , correspond to steps  1708  and  1720 , respectively. 
     To facilitate an understanding of the processing performed by the application program in order to further appreciate the present invention, the application program processing depicted in  FIG. 20  is directed at a specific example.  FIG. 20  assumes an application program communicating with a DOM server using a configuration database configured as described earlier in relation to  FIGS. 6 through 16 . Particularly,  FIG. 20  describes the request and objectization for a GetCustomerInfo CS transaction so configured. Further, a GetCustomerInfo CS transaction executed in accordance with  FIGS. 6 through 16  results in communication of a CS transaction response message data stream from the DOM server to the application program. The GetCustomerInfo response data stream is constructed of tokens as depicted and described in relation to  FIG. 18 . Accordingly, references to tokens in the discussion that follows refer to  FIG. 18 . 
       FIG. 20  does not depict all of the steps in the objectization of the data stream depicted in  FIG. 18 .  FIG. 20  depicts as much as is necessary to fully reveal the fundamental operation of the objectization process without unnecessary repetition. It is noted that complete objectization of the data stream depicted in  FIG. 18  in accordance with the fundamental operation described in  FIG. 20  would produce the complete object hierarchy depicted and described in relation to  FIG. 19 . 
       FIG. 20  graphically segregates the processing performed by user-written procedural logic in column  2010 , the processing performed by user-declared and customized customer root folder object  1900  in column  2020 , the processing performed by objects instantiated as a result of the objectization process in column  2030 , and the processing performed by FDO generalized objectization service code in column  2040 . Column  2040  represents program code incorporated into an application program from development library files such as library  252  as depicted and described earlier in relation to  FIG. 2 . Such program code may be physically incorporated into objects represented in columns  2020  and  2030 , but is identified separately here in order to facilitate an understanding of the presently described embodiment. 
     Step  2051  of  FIG. 20  shows user application code  2051  sending a CS transaction request to the DOM server. The request identifies GetCustomerInfo as the desired transaction. The request also includes an atmCardCode data item as required by the configuration for the GetCustomerInfo input message. The DOM server processes the request and returns a response message to user code  2010  in the form of data stream token  1800 . 
     In step  2053 , the application program prepares for objectization by instantiating a folder object to serve as the root for an object hierarchy. The application program expects a customer-rooted hierarchy out of the GetCustomerInfo transaction and so instantiates a folder object  1900  of customerFolder type. 
     In step  2055 , user written program logic  2010  invokes the deserialize method of the customerFolder object  1900 . The deserialize method is a request for objectization. User program logic includes data stream token  1800  as an input to the deserialize method. 
     In step  2057 , the customerFolder object  1900  invokes FDO service code  2040  to deserialize the data stream token. From this point forward, FDO service code  2040  drives the objectization (deserialize) process. Bracket  2099  indicates the long lifetime of the FDO service code deserializeo function. While FDO service code drives the process, it enlists the help of other objects along the way. Notably, FDO service code will invoke the services of folder-type objects and primary-type objects to assist in forming and filling the portions of the object hierarchy they contain. This is illustrated in the steps that follow. 
     FDO service code  2040  progressively unpeels data stream token  1800  to proceed with objectization. In step  2059 , FDO service code  2040  passes data stream token  1800  to CustomerFolder object  1900 , with specific reference to family token  1810 . The CustomerFolder object  1900  responds to the FDO service code  2040 , indicating that it is aware of a folder-type object associated with the specifically-referenced token  1810 . 
     Because of the affirmative response in step  2059 , FDO service code  2040  turns around in step  2061  and instructs the CustomerFolder object  1900  to instantiate an object that can embody ensuing tokens in the data stream. FDO service code  2040  passes data stream token  1800  to CustomerFolder object  1900 , with specific reference to token  1820 . The CustomerFolder object  1900  unnests the tokens embedded within token  1820  to ultimately compile a list of the field types represented in the leaf tokens contained within business object token  1840 . CustomerFolder object  1900  uses the compiled list of field types to determine that a Customer-type object should be used to embody the data items from token  1840 . This object-type selection process is discussed in detail in reference to  FIG. 21 . Accordingly, CustomerFolder object  1900  instantiates Customer-type object  160  in step  2063 . Instantiation of Customer object  160  causes instantiation of other objects in the hierarchy immediately depending from it, namely, leaf-type objects  1910 - 1916 , and AccountFolder object  1920 . CustomerFolder object  1900  passes the identity of newly instantiated Customer object  160  to FDO service code  2040 , to conclude the makeObject( ) request of step  2061 . 
     FDO service code continues to unpeel the tokens embedded in data stream token  1800 . In step  2065 , FDO service code  2040  passes data stream token  1800  to CustomerFolder object  1900 , with specific reference to the first leaf token embedded in Customer business object token  1840 . Customer object  160  responds to the FDO service code  2040 , indicating that it is not aware of a folder-type object associated with the specifically-referenced token. 
     Because of the negative response in step  2065 , FDO service code  2040  turns around in step  2067  and instructs the Customer object  160  to populate an object that embodies the subject leaf token from business object token  1840 . Leaf object  1910  is populated with the data item and metadata from the subject leaf token. Steps  2065  through  2067  are repeated for each leaf token embedded within business object token  1840 . 
     FDO service code continues to unpeel the tokens embedded in data stream token  1800 . In step  2069 , FDO service code  2040  passes data stream token  1800  to Customer object  160 , with specific reference to family token  1850 . Customer object  160  responds to the FDO service code  2040 , indicating that it is aware of a folder-type object associated with the specifically-referenced token  1850 . 
     Because of the affirmative response in step  2069 , FDO service code  2040  turns around in step  2071  and instructs the AccountFolder object  1920  to instantiate an object that can embody ensuing tokens in the data stream. FDO service code  2040  passes data stream token  1800  to AccountFolder object  1920 , with specific reference to token  1830 . The AccountFolder object  1920  unnests the tokens embedded within token  1820  to ultimately compile a list of the field types represented in the leaf tokens contained within business object token  1860 . Processing at this point proceeds after the fashion described in relation to step  2061 . As FDO service code  2040  progressively unpeels the tokens in the data stream and iteratively and recursively makes and populates objects, the object hierarchy depicted in  FIG. 19  is completely formed and filled. When the tokens of the data stream are exhausted, the FDO service code objectization process started at step  2057  completes. The user application program logic  2010  may then proceed to take full advantage of the object hierarchy and the data items it embodies. 
       FIG. 21  is a flowchart showing an object-type selection process used by folder-type objects when processing a makeObject( ) request. This process was referred to earlier in reference to objectization process step  2061  of  FIG. 20 . In step  2110  of  FIG. 21 , the folder begins the object-type selection process by examining the data stream token contents to identify all of the data items contained therein for the primary object to be created. The number of data items may be less than the number of data items configured for the associated CS transaction output message, but can never be more. (This is because the list of data item elements in the output message represents the union of the sets of field types for all possible object types in the family.) 
     In step  2112 , the folder sets up to perform a loop through all of the object types in the family by pointing to the first one. In step  2114 , the folder performs a preliminary test to quickly ascertain whether the currently considered object type has the potential for success. This step is performed in one embodiment by comparing the number of inbound data items to the number of data items in an object of the currently considered object type. If it is greater, the currently considered object type is not “large” enough and processing proceeds to step  2122 . If it is less than or equal, a detailed comparison of the field types in the inbound data stream and the field types (attributes) of the object type is made in step  2116 . In step  2118 , the folder then determines whether the comparison is successful. In the presently described embodiment, the comparison is successful if every inbound data item is represented in the attributes of the currently considered object type. If the comparison is unsuccessful, processing resumes at step  2122 . If the comparison is successful, differences between the list of inbound data items and the list of object type attributes may be recorded in step  2120 . 
     Step  2122  determines whether any other object types in the family remain to be considered. If so, step  2124  identifies the next candidate object type for consideration and processing loops back to step  2114 . If not, processing continues at step  2126  where the folder determines whether any of the candidate object-types is a successful match. If not, failure is indicated in step  2128 , object-type selection is finished and the report of failure is available for subsequent processing in step  2132 . If any candidate has been successful, step  2130  determines the best candidate. In the presently described embodiment, the best candidate is the first successful object type in the list having the smallest number of attributes in excess of the number of field types in the inbound data stream. Once identified, step  2132  informs subsequent program logic of the object type to be used for primary object instantiation. 
     In an embodiment that supports multiphase object initialization, this same object-type selection process could be used to provide a best-fit object type for a primary object augmented by multiphase initialization with additional data items. In this case, step  2110  determines a list including not only inbound data items, but data items populated in the preexisting primary object, as well. 
       FIG. 22  is a class diagram including a folder class and family registration data. This figure illustrates the class structure used in the presently described embodiment of a client application program to implement the exemplar savings account and bankcard account real-world entities in an object-oriented fashion. This class structure further illustrates support for the objectization process described in reference to  FIGS. 20 and 21 . 
     AccountFolder class  2200  is defined by the application programmer. An object oriented language such as C++ is used. The application programmer defines the AccountFolder class by coding an FDOfolder class template  2202  with the familyName parameter, “Account.” In the presently described embodiment, source code representing the FDOfolder class template is contained within generalized development file libraries because a folder-type object lends itself to generalization, i.e., many different folder-type objects may be needed, all of which perform in the same way. 
     FDOfolder class template  2202  contains program code to perform the functions previously described for a folder-type object, including the object-type selection, instantiation and management of related primary objects. The application programmer implicitly or explicitly declares an AccountFolder as static, so that one AccountFolder is built into the executable version of the client program. The one AccountFolder in storage satisfies the needs for the entire client application program. The static AccountFolder serves as a repository for information about all of the object-types (classes) belonging to the family during program execution. In this example, the AccountFolder includes family registration information  2210  about a savingsAccount family object-type and a bankcardAccount family object-type. 
     The application programmer defines Account class  2220 . Account class  2220  serves the purposes of channeling the functionality of FDOnode class  2230  to classes deriving from it, via inheritance, and relating classes deriving from it to the static execution copy of AccountFolder  2200 . The application programmer defines the Account class by coding a class declaration specifying inheritance from FDOnode class  2230 . Code representing the FDOnode class is contained within generalized development file libraries in the presently described embodiment. FDOnode class  2230  includes program code that causes any inheriting class, e.g.,  2220 , to place certain information about itself into the family registration information of a related folder for program execution. In the presently described embodiments, definitions of data items with a static storage class achieve this objective. Declaration of the static storage class in source code causes the compiler to generate executable code in the prologue of the resulting program that populates the family registration data  2210  of the AccountFolder when the program first initializes. The operational charateristics of static storage data are well understood in the art. 
     The application programmer associates Account class  2220  to AccountFolder class  2200 . The association may be made explicitly or may be made implicitly, e.g., by the common “Account” portion of the two class names. 
     The application programmer also specifically codes the declarations and definitions for savingsAccount class  2223  and bankcardAccount class  2225 . These classes specialize generic Account class  2220 , adding new object-types to the object-type family represented by AccountFolder class  2200 . Class savingsAccount  2223  underlies execution object  162  shown in  FIG. 19 . 
     In the presently described embodiment, savingsAccount class  2223  definition includes code to incorporate leaf-type objects as data members of the class for number, type, status, and balance data items. The inclusion of the four leaf-type objects is depicted in  FIG. 22  by the association shown between savingsAccount class  2223  and FDOleaf class  2240 . The corresponding execution-time objects are shown by leaf objects  1930 ,  1932 ,  1934 , and  1936  in  FIG. 19 , respectively. 
     Class bankcardAccount  2225  underlies execution object  164  shown in  FIG. 19 . In the present embodiment, bankcardAccount class  2225  definition includes code to incorporate leaf objects as data members of the class for number, type, status, balance, and creditLimit data items. The inclusion of the five leaf-type objects is depicted in  FIG. 22  by the association shown between bankcardAccount class  2225  and FDOleaf class  2240 . The corresponding execution-time objects are shown by leaf objects  1940 ,  1942 ,  1944 ,  1946 , and  1948  in  FIG. 19 , respectively. 
     Family registration information  2210  depicts the execution-time contents for savingsAccount class  2223  and bankcardAccount class  2225 . Family registration information  2210  may hold similar information for Account class  2220 , itself, and any other classes deriving from it. Family registration information is principally used in the objectization process for selecting the type of object within the family to embody inbound data items from a data stream, as described earlier in reference to  FIG. 21 . Family registration data  2210  contains the list of candidate object-types and the data items (attributes) belonging to each. Table  2212  contains the list of candidate object-type names in column  2212   a . For each candidate object-type name in column  2212   a , column  2212   c  holds a pointer to a list of data item names belonging to the candidate object-type. The pointer in column  2212   c  for the savingsAccount object-type points to attribute name list  2214  containing the attributes names “number,” “type,” “status,” and “balance.” The pointer in column  2212   c  for the bankcardAccount object-type points to attribute name list  2216  containing the attributes names “number,” “type,” “status,” “balance,” and “creditLimit.” When an object of AccountFolder type receives a makeObject( ) request during execution, the data item names contained in the “field type” tokens (e.g.,  1872  of  FIG. 18 ), embedded within the leaf-type tokens (e.g.,  1871  of  FIG. 18 ), embedded within the business object type token (e.g.,  1870  of  FIG. 18 ) presented with the makeObject( ) request, are compared against lists  2214  and  2216  of  FIG. 22  by AccountFolder logic represented by process step  2116  of  FIG. 21 , to select the object-type for the programming object to embody the data items of the business object token (e.g.,  1870  of  FIG. 18 ). If exemplary business object token  1870  of  FIG. 18 , were to originate from the SINQ screen of SS transaction GetSavings depicted and described in relation  FIG. 9 , savingsAccount object-type will be chosen over bankcardAccount object-type because the list of data item types from the SINQ screen processing is an exact match to the list of attributes of the savingsAccount object-type. Because exemplary business object token  1870  of  FIG. 18 , originates from the BINQ screen of SS transaction GetBankcard depicted and described in relation  FIG. 10 , bankcardAccount object-type will be chosen over savingsAccount object-type because the list of data item types from the BINQ screen processing is an exact match to the list of attributes of the bankcardAccount object-type, and the attributes of the savingsAccount object-type are insufficient to contain the data items from the BINQ screen processing. These results are based on default object-type selection rules incorporated into the presently described embodiment. 
     As an alternative to the default object-type selection rules, the presently described embodiment provides for the application programmer to substitute custom object-type selection logic. The application programmer defines a function for each family object-type that receives at least the relevant business object-type token data from the data stream for its input, and provides as its response an indication whether it can embody the business object-type token data items. The application programmer incorporates code into the program to register each object-type selection function in column  2212   b  of family registration information  2210  alongside the name of the object-type to which the function relates. Functions must be registered for all or none of the family object-types listed in table  2212 . If functions are registered, the object-type selection process of  FIG. 21 , is replaced with the object-type selection process depicted in  FIG. 23 . The use of functions to replace default object-type selection processing permits the selection of object-type using criteria other than the list of inbound field types alone. For example, the value of the field (i.e., the data item) in a particular instance of a message can factor into the determination of object-type; e.g., number fields beginning with “51” indicate a savingsAccount object. The flexibility in run-time object-type determination represents a further advantage of the present invention. 
     It is noted that numerous examples have been used throughout this detailed description to explain the operation of an embodiment employing the present invention. The discussion of the examples principally described data access operations for retrieving data from a data source, i.e., inquiry transactions. One skilled in the art recognizes the obvious modifications required of the examples shown to describe employment of the present invention for data access operations that add or update to a data source. In general, the flow of data items is reversed. 
     Various modifications to the preferred embodiment can be made without departing from the spirit and scope of the invention. Thus, the foregoing description is not intended to limit the invention which is described in the appended claims in which: