Abstract:
A tool for the development of multiple-table database applications for client/server environments automates both capture of system requirements and code production. A client portion of a multiple-table, client/server database application for processing requests against a server database, is developed by first storing in a repository a description of the server database describing database entities within the server database and relationships between those database entities. Representations of the database entities are displayed, and an application drawing window is provided. The user drags and drops within the application drawing window one of said representations that represents a particular database entity. The tool then creates within the repository an entry for the particular database entity, and draws within the drawing window a representation of the particular database entity. For each database entity for which an entry within the repository has been created, the tool checks the description of the server database stored in the repository to determine whether a relationship exists between the particular database entity and the database entity being checked. If a relationship does exist between the particular database entity and the database entity being checked, the tool then creates within the repository an entry for that relationship, and draws within the drawing window a connector representing that relationship. The foregoing drag-and-drop sequence is repeated multiple times. When the design is complete, the tool, using information stored in the repository, automatically generates the client portion of the multiple-table, client/server database application.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to software development tools for developing client/server software, particularly multiple-table database applications for client/server environments. 
     The development of multiple-table database applications for client/server environments has been a laborious, time-consuming task requiring a high level of expertise. Such applications are custom-developed to the specifications of a particular customer. Hence, unlike the development of shrink-wrapped software which may also require a high level of programming expertise, the development of multiple-table database applications for client/server environments requires in addition expertise in the business of the customer. 
     Capturing the requirements of the application is in itself a complex task, involving significant analysis and design. When the resulting specification is approved, then the work of actual programming begins. Once coding has proceeded to a significant degree, it becomes extremely difficult to makes changes to the application. This approach to client/server development may therefore be termed &#34;the waterfall approach&#34;--once development has proceeded beyond a certain point (&#34;the waterfall&#34;), it is difficult or impossible to go back or change course. 
     What is needed, therefore, is a tool for the development of multiple-table database applications for client/server environments that simplifies both capture of system requirements and code production in a way that greatly reduces the time, cost and expertise required to develop complex client/server applications. The present invention addresses this need. 
     SUMMARY OF THE INVENTION 
     The present invention, generally speaking, provides a tool for the development of multiple-table database applications for client/server environments that automates both capture of system requirements and code production. In accordance with one embodiment of the invention, a client portion of a multiple-table, client/server database application for processing requests against a server database, is developed by first storing in a repository a description of the server database describing database entities within the server database and relationships between those database entities. Representations of the database entities are displayed, and an application drawing window is provided. The user drags and drops within the application drawing window one of the representations that represents a particular database entity. The tool then creates within the repository an entry for the particular database entity, and draws within the drawing window a representation of the particular database entity, e.g., a form to be generated. For each database entity for which an entry within the repository has been created, the tool checks the description of the server database stored in the repository to determine whether a relationship exists between the particular database entity and the database entity being checked. If a relationship does exist, the tool then creates within the repository an entry for that relationship, and draws within the drawing window a connector representing the same. Each connector may represent a Form Transition, for example. The foregoing drag-and-drop sequence is repeated multiple times. When the design is complete, the tool, using information stored in the repository, automatically generates the client portion of the multiple-table, client/server database application. Within the client portion of the multiple-table, client/server database application, when data from a particular database entity is displayed, if a user inputs a specified command, data from a related database entity is displayed. Further features of the invention include automatic Master/Detail construction and automatic multi-form synchronization. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The present invention may be further understood from the following description in conjunction with the appended drawing. In the drawing: 
     FIG. 1 is a diagram illustrating the overall process of developing a database application using the present tool; 
     FIG. 2 is a screen display of a repository browser window used to quickly locate database entities to be used in designing the database application; 
     FIG. 3 is a screen display of an application designer window into which database entities from the repository browser are dragged and dropped; 
     FIG. 4 is a screen display of the application designer window following the drag-and-drop design process; 
     FIG. 5 is a screen display showing a Form and Grid Creation dialog in response to which the user confirms or disconfirms design actions of the tool taken in response to the user&#39;s drag-and-drop manipulation of database entities; 
     FIG. 6 is an entity-relationship diagram of the database used to capture information about the design of the database application; 
     FIG. 7 is a screen display showing a Recordsource Form Properties sheet displaying the contents of a node within the application drawing window of FIG. 4 and from which the Recordsources of the form and their status as dependent or independent may be observed; 
     FIG. 8 is a screen display showing a Form Transition Properties sheet used to edit the properties for a Form Transition; and 
     FIG. 9 is screen display showing a Master/Detail form in a multiple-table database application. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description describes various innovative features of a tool for the development of multiple-table database applications for client/server environments. The development tool is commercially available from the present assignee under the trade name Vision Builder™. In the following description, the various terms are used in accordance with definitions as follows: 
     Application generator: a Vision Builder tool that uses repository information to automate generating complete, executable multiple-form applications without requiring any 4GL coding. 
     Child table: a table from the &#34;many&#34; side of a one-to-many relationship. 
     Data model: a description of a database in terms of tables, columns (lengths and types), primary keys and foreign keys, relationships, and QueryDefs. A one-to-many relationship is defined using a primary key from the one (&#34;parent&#34;) side, plus a foreign key from the many (&#34;child&#34;) side. 
     Display form: a form table style that uses GUI fields and/or controls such as text boxes, check boxes, combo boxes and so on (in contrast with a grid style that presents data in a spreadsheet-like style of rows and columns). When a display form also presents related child data within a grid on the same form, it is referred to as a Master/Detail. 
     Form Transition: a property that allows a Recordsource to feed the Root Recordsource of another form, as well as to show that other form. 
     Form: a window designed to play a specific role in a program&#39;s visual interface. 
     Form table: represents the information necessary to generate a Recordsource used to see related data, either on the same form or some target form. 
     Grid form: a form that displays information in row/column format. A Grid form shows a set of database records in a spreadsheet-like format (many records with little detail about each). The user can choose one of the records to access a display form with information about that selected record. 
     Master/Detail: a form style that presents table data in a master GUI display and data from child rows in a grid embedded on the same form. Typically the master and detail&#39;s aspects are dynamically linked such that changing to a different master record summons the applicable child detail. 
     Parent: a table from the &#34;one&#34; side of a one-to-many relationship. 
     Pick: a Vision Builder operation that allows users to select information from one form and copy it into foreign key fields on another form. 
     Query By Forms (QBF): in Vision Builder, a Query Specification form on which users enter search criteria to retrieve specific information from database tables. 
     QueryDef: a named SQL query of joins and projections of Base Tables and/or other QueryDefs created by the user and stored in the database. A QueryDef object makes it convenient to test and store information needed to create recordsets that are used often. 
     Recordsource: a collection of records selected from a query or table and presented on a form. A Root (or Master) Recordsource is always displayed and is populated by another form when this form is part of a Form Transition. An Independent Recordsource does not depend on any other Recordsources in the form for its records. A Dependent Recordsource depends on other Recordsources in the form and has a property called &#34;srcFormTableNum&#34; that refers to another Recordsource on this form. In particular, when a new row becomes current in the source Recordsource, the system issues a SQL query to retrieve the related rows in each Dependent Recordsource. This SQL query is constructed using the key fields from the source Recordsource as selection values to corresponding columns in the Dependent Recordsource. The corresponding columns are typically derived from a relationship between the tables. 
     Relationship: a superset of relationships defined between Base Tables by the application developer and relationships involving QueryDefs, which are computed by the system. 
     Repository: a database file such as a .MDB file that contains all of the data definitions for Base Tables, QueryDefs and applications. 
     Root table: a table on a form that controls or synchronizes record display and updates behavior of other, related tables on the form. 
     Start-up form: in Vision Builder, a form that is created from definitions on the Application Designer and Form Property sheets. When an application is built, a start-up form is automatically created with menu items and toolbar buttons to access forms that were dropped on the diagram (and their underlying database tables). 
     Surrogate ID (surrid): in Vision Builder, a unique identifier for every object in Vision Builder applications that allows the system to keep client and server components synchronized. 
     Table: a superset of Base Tables and QueryDefs. Base Tables and QueryDefs share a Name Space; i.e., each table name is unique. 
     Template: a pre-built application component consisting of both graphical controls (such as combo boxes and radio buttons) and code governing form/control behavior. When a client application is generated, Vision Builder templates, or user-customized templates, are included. 
     Transition: the &#34;call&#34; relationship between the tables represented by forms on the application diagram; by default, the arrow points to the &#34;many&#34; or &#34;child&#34; table in a one-to-many or parent/child relationship. Curved arrows with the same beginning and end point represent self-relationships. 
     Trigger: a mechanism for associating an insert, update, or delete statement on the database server with the server code that executes in response to that server event; triggers are executed by the database when specific types of data manipulation commands (insert, update, delete) are performed on specific tables. 
     Broadly speaking, the development of multiple-table database applications for client/server environments may be divided into two phases. During a capture phase, the development tool captures information concerning the design of the application as the user &#34;draws&#34; the application in a drawing area using drag-and-drop techniques. During a subsequent generation phase, the development tool generates client and server code to realize the application. 
     The application runs against a database server, such as Oracle 7, for example, or any of a number of ODBC (Open Database Connectivity)-compliant database servers, such as Sybase, Informix, etc. 
     The generation of database server code is known in the prior art. ssentially, the user specifies declarative business rules describing the undamental server-side behavior of the system. The development tool generates corresponding database trigger code for the database server. Since this aspect of client/server automation is known, it will not be further described. 
     The present development tool achieves significant advances in the generation of client code, described herein in detail. The target language for the client code is preferably a forms-based, 4GL language such as Visual Basic, Powerbuilder, SQL for Windows, etc. Hence, from the application design information captured during the capture phase, the development tool during the generation phase generates a set of forms together with 4GL code that controls the behavior of those forms. An overview of the development process using the present development tool is shown in FIG. 1. Referring to FIG. 1, in order to generate a multi-form application to run against a database server 100, a local database, or repository 110, is created. Within the repository, a data model 111 of the server database is created. To this data model is added additional &#34;layers&#34; of information, including business rules 113 (touched upon previously) and application definition information 115. The application definition information 115 is captured as the user draws the application within an application drawing area 120 (displayed on a computer screen, not shown) using drag-and-drop techniques. 
     The application definition information 115 may itself be in the logical form of a database. In a preferred embodiment, an application is described as a collection of table rows related in one-to-many fashion. An application describes a multi-form program and is represented by a table row within a table VSVBApps 116. (&#34;VSVB&#34; stands for &#34;Vision Software Vision Builder.&#34;) A database may contain several applications, each of which is represented by an application drawing (120). An application may contain many forms, each of which is described by a single row within a table VSVBAppForms 117. A form may contain multiple tables, each of which is described by a table row within a table VSVBAppFormTbls 118. Finally, each table may respond to user input to cause a transition to another form. Each transition is described by a table row within a table VSVBAppFormShows 119. 
     The present development tool may be built upon and leverage the capabilities of existing popular software packages. In an exemplary embodiment, Microsoft Access is used as the repository. Microsoft Access is a relational database management system that is part of the Microsoft Office Pro application suite. Also in an exemplary embodiment, the multiple-table database application is generated in Microsoft Visual Basic; i.e., the application is a Visual Basic project. As described previously, Visual Basic is a 4GL, forms-based programming language. Of course, other database management systems and other target 4GL programming languages may be used. 
     An application in Visual Basic typically contains two types of code: form-specific code and generic code. Code that pertains to a particular form is form-specific code and, in Visual Basic, is stored as part of that form. Other code (stored as &#34;modules&#34;) is more general in nature. In the case of the present tool, this includes, for example generic code that, when a row becomes current, synchronizes each Dependent Recordsource (i.e., opens Dependent Recordsources using parameter values from the source Recordsource). Referring still to FIG. 1, the generic code constitutes a run-time library 130 that is &#34;included&#34; as part of the final application. The form-specific code is generated by application generation code 140 from templates, pre-built application components consisting of both graphical controls and code governing form/control behavior. The result is a set of forms and 4GL code realizing the desired client application. 
     Because no manual coding is required, the application can be easily modified, repeatedly if necessary, and regenerated. The &#34;coding waterfall&#34; problem characteristic of the prior art is thus avoided. 
     In general, using the present development tool, development proceeds in accordance with an iterative development cycle that may be loosely divided into three cycles: application design, business rules definition and customization. In the application design cycle (particularly the subject of the present description), the developer and the customer design the application by drag-and-drop and implement the application using templates. In the business rules definition cycle, the developer and the customer design and implement the application&#39;s business logic. During the customization cycle, the developer and the customer customize the application&#39;s appearance, behavior and business logic if needed. Development steps in accordance with the present development tool contrast sharply with development steps in accordance with prior art methodologies, as shown in the following Table 1: 
     
                       TABLE 1______________________________________TRADITIONAL       PRESENTDEVELOPMENT STEPS DEVELOPMENT TOOL STEPS______________________________________Talk to customer and gather data             Talk to customer and gather datamodel information.             model information.Go away. Design the data model and             Go away and build data model ordevelop the application forms.             import the customers existing data             model from MS Access or their             DBMS.Review forms with customer and             Meet with customer and generateexplain how the forms will             application. Review forms, forminteract. Receive feedback.             flow, and data entry procedures.             Make changes with dialogs and             regenerate the application until             customer is satisfied.Go away. Make any required form             Gather business requirements.changes. Write the form flow codeand application logic.Review application with customer             Go away and implement businessand explain the database procedures             rules by filling out dialogs. Testand how the interface will work.             deploy the application data modeReceive feedback. and business rules to the database             server.Go away. Make the required changes             Review application with customer.to the code. Write business logic             Make changes and regenerate thecode.             application as needed until your             customer&#39;s requirements are met.Review application with customer             Go away and make finaland show data entry procedures.             customization.Receive feedback.Go away. Make required changes to             Get customer approval and deliverthe code. Review with customer.             to customer.(This step may be repeated severaltimes.)Get approval. At this point, manydevelopers must rewrite the wholeapplication to ensure scalability andclient/server performance.Deliver to customer.______________________________________ 
    
     The first step in developing a client/server database application using the present tool is to produce a data model of the target database. In a preferred embodiment, the data model takes the form of a database within a database management system such as Microsoft Access. The data model may be obtained in various ways. It may be entered directly into the database management system, or the target database may be converted into a database within the database management system. Also, CASE (Computer-Aided Software Engineering) tools may be used produce a data model which may then be imported into the database management system. The data model is composed of Base Tables, query definitions, or QueryDefs, etc. The data model becomes the basis for the repository, i.e., the database 110 of FIG. 1 that is used to capture and store all of the required information to generate the database application. 
     Once the data model has been created within the database management system, the user may begin designing the database application. To do so, the data model is opened so as to enable the various entities within the data model to be viewed within a GUI (Graphical User Interface) window. In a preferred embodiment, the tool provides a &#34;repository browser&#34; (FIG. 2) that enables database entities within the data model (Base Tables, QueryDefs, etc.) to be quickly and easily located. An application drawing window is also opened, as shown in FIG. 3. The user then drags and drops database tables (as defined above) onto the design area of the application drawing window. 
     As the user drags and drops database tables into the application drawing window, the tool, based on the entity relationships stored in the data model, makes intelligent inferences about the user&#39;s intentions and forms relationships between the database tables and illustrates them within the application drawing window (FIG. 4). As these relationships are formed, the user may be asked to confirm or discontirm, using a Form and Grid Creation dialog (FIG. 5). Or the user, having become experienced with the tool, may select to have the tool proceed without presenting the dialog. 
     As design of the application proceeds, information concerning the database tables in the application design window and the relationships between them is stored in the repository in the form of a database, the structure of which is shown in FIG. 6. A row is created within a VSVBApps table 610 for each separate application drawing, the row having the columns shown underneath the caption VSVBApps in FIG. 6. Each application may have multiple forms. For each form in the application, a row is created within a VSVBAppForms table 620, the row having the columns shown underneath the caption VSVBAppForms in FIG. 6. Each form in the application may display data from multiple tables, in &#34;Master/Detail&#34; format, for example, as shown in FIG. 9. The tables are the actual source of data within the application, while the forms each function as a &#34;shell&#34; to display the data. For each table, or Recordsource, in the application, a row is created within a VSVBAppFormTables table 630, the row having the columns shown underneath the caption VSVBAppFormTables in FIG. 6. Finally, for each table used to populate a form with data, different selections by a user of different data fields may result in different forms being called up and shown. That is, each table may have multiple Form Transitions (as that term is defined, consistent with its use within the Visual Basic programming language) or the equivalent. For each Form Transition in the application, a row is created within a VSVBAppFormShows table 640, the row having the columns shown underneath the caption VSVBAppFormShows in FIG. 6. 
     Notice that, beginning on the left-hand side of FIG. 6 with the VSVBApps table, each table bears a &#34;one-to-many&#34; relationship with the next table to the right, this one-to-many relationship being denoted by &#34;1&#34; on the one side (parent side) of the relationship and by &#34;∞&#34; on the many side (child side) of the relationship. The primary key of the VSVBApps table, surrid for &#34;surrogate ID,&#34; is added to the VSVBAppForms table as a foreign key, relating each form back to the application in which it appears. The primary key of the VSVBAppForms table is surrid and formNum. Both surrid and formNum are required to uniquely identify a form. Each succeeding table has as foreign keys the foreign keys and primary key of the preceding table, and has its own primary key, all of these keys being required to uniquely identify a particular row within that table. 
     Given an application, i.e., a row within the VSVBApps table identified by a unique surrid, it is a trivial exercise to find all the forms that belong to that application. Say, for example, that surrid=27. A simple database operation may be used to search the forms table, VSVBAppForms, to find all the forms that have surrid=27. 
     Many of the particular columns within the rows shown in FIG. 6 are not important to an understanding of the present invention and therefore are not described in detail. Brief descriptions of the fields are included as Appendix I. Of particular interest, however, are the &#34;reln&#34; (relationship) columns within the VSVBAppFormTables table--relnExtSurrid, relnIsFromParent, relnWhereClause, and reInParms. The field rellIsFromParent denotes the direction of the relationship, either from parent (e.g., from Department to sub-departments) or from child (e.g., from Department to super-department). 
     Whereas it is a simple matter, given an application, to find its forms, a more subtle problem is to determine what data should be used to populate a particular form. In other words, the system must be able to determine from what form table another form table gets its parameters in constructing a SQL query to retrieve data for that Recordsource, and which fields are those parameters. To take a simple example of a database having a CUSTOMER table that transitions to an ORDERS table, when a new customer is added and the transition to ORDERS is executed, the system must know to display the orders of the new customer, not the orders of the customer displayed previously. The &#34;reln&#34; columns store the information necessary to ensure proper synchronization of this type between forms. 
     In other words, within a particular form, a Dependent Recordsource, or form table, must know the Recordsource (dependent or independent) from which it depends. 
     At Definition Time, doubling clicking on a form within the application drawing window causes the form&#39;s Form Properties sheet (FIG. 7) to be displayed, from which one may observe whether a Recordsource, or form table, is dependent or independent. In FIG. 7, it may be seen that CUSTOMERS is an Independent Recordsource (i.e., appears at the top of the hierarchy for the form), and that ORDERS depends on CUSTOMERS. In FIG. 6 therefore, within the row of VSVBAppFormTables corresponding to ORDERS, the field srcFormTableNum with have a value that refers to CUSTOMERS (i.e., &#34;1&#34;--the first Recordsource in this form). 
     The knowledge that ORDERS depends on CUSTOMERS, however, is not by itself sufficient to populate ORDERS with the correct data. The system must also know which fields within CUSTOMERS and ORDERS are matching. In technical terms, relnExtSurrid identifies the relationship of the base table or (QueryDef) between the driving and the driven data controls in the repository and is used to compute the relnWhereClause. The relnWhereClause (which supports multiple keys) identifies the join between the primary and foreign keys for the relationship, and relnParms lists the parameters and their data types for the one side of the relnWhereClause that is a parameter. For example, in the case of CUSTOMERS and ORDERS, assuming CName is the primary key in CUSTOMERS and CustName is the corresponding foreign key in ORDERS then, for the ORDERS Recordsource, the relnWhereClause is &#34;CustName= ?Cname!&#34;; the relnParms are &#34; ?Customer ID!&#34;. At runtime, a SQL query is created by substituting the current value of the source Recordsource (CUSTOMER) into the Dependent Recordsource&#39;s parameter using a column name the same as that specified in the relnParms. The SQL query is prefaced by &#34;select * from&#34;. The source Recordsource is indicated by srcFromTblNum. 
     For example, at runtime, suppose the user positioned to a new customer &#34;ACME&#34;. The relnWhere and reinParms values are used, along with the Customer row value, to construct this SQL query: 
     
         select * from ORDERS where CustName=&#34;ACME&#34;. 
    
     Resulting rows are displayed in the ORDERS grid on the form. 
     Note that the database table to be queried is given in VSVBAppFormTables (FIG. 6) by the field tblName, and the foreign key query value is given by the primary key value of the row srcFormTableNum. 
     The foregoing notion is fundamental and is propagated throughout the generated application such that Dependent Recordsources remain in sync with the Recordsources from which they depend. Furthermore, although the case of a single Dependent Recordsource has been described, a Recordsource may have multiple Dependent Recordsources, some are all of which may have their own Dependent Recordsources, etc. For example, ORDERS may depend from CUSTOMERS and ITEMS may depend from ORDERS, and PAYMENTS may depend again from CUSTOMERS, etc., in nested fashion. 
     A similar principle of operation applies to Form Transitions, each of which is represented by a row in the VSVBAppFormShows table in FIG. 6. At runtime, a Form Transition is activated from one form (by double clicking, menu selection, etc.) so as to launch yet another form. Form Transitions are represented in the application drawing window as arrows. At Definition Time, doubling clicking on an arrow within the application drawing window causes the Form Transition Properties sheet (FIG. 8) to be displayed. Again, the indentation of a Form Transition underneath another form indicates that the Form Transition will obtain its data from that form. In FIG. 8, it may be seen that the Form Transition ORDERS is indented underneath the Dependent Recordsource ORDERS(placedOrders). Therefore, when the Form Transition ORDERS is executed, the table ORDERS(placedOrders) will be used to populate the form. In others words, the user picks an order from the table ORDERS(placedOrders) and the Form Transition ORDERS is then started with that order. In Visual Basic terms, a reference to the RecordSet driving the CUSTOMER.ORDERS grid is placed in the ORDERS Data Control to drive ORDER Scalar fields. 
     From the foregoing discussion, it will be appreciated that an important feature of the present tool is the ability to build multiple-table forms with nested Recordsources, which are themselves inferred and built on the basis of database relationships stored in the repository. The tables illustrated in FIG. 6 contain all of the information required to generate the final application. Equally important, however, is the manner in which the data in FIG. 6 is captured from user manipulation of database entities, i.e., from the user drawing the application. The tool must be provided with certain intelligence in order to determine whether, based on the particular manipulations observed, the user wants to create a Master/Detail display, etc. 
     Referring again to FIG. 5, the tool&#39;s inferences about the user&#39;s intent based. on the user&#39;s manipulation of database entities is normally presented to the user in the Form and Grid Creation dialog. Consider first the frame 510 within the dialog, Automatic Master/Detail Creation. Master/Detail creation pertains to parent/child relationships stored within the repository. In the case of CUSTOMERS and ORDERS, for example, CUSTOMERS is the parent and ORDERS is the child. When the user first drags and drops CUSTOMERS and then drags and drops ORDERS, the tool infers that the user wants to create a Master/Detail form on which displaying a customer causes a list of that customer&#39;s order to also be displayed. 
     To accomplish this result, when a database entity is dropped, the system, prior to displaying the Form and Grid Creation dialog of FIG. 5, first &#34;looks around&#34; at the other entities that have already been dropped to see if there are any forms for which a parent of the database entity being dropped is the Root Recordsource, i.e., is at the top of the form hierarchy. If so, then the &#34;child&#34; table (e.g., ORDERS) &#34;finds&#34; its parent table (e.g., CUSTOMERS), and is added within the database of FIG. 4 as a grid on the form of the parent table(s). The parent tables are listed within the Select Grids for Parent Displays box 511 in FIG. 5. In the example of CUSTOMERS and ORDERS, an entry such as CUSTOMERS.ORDERSGrid would be listed here, indicating that an order grid has been added to the customer display. 
     Although the foregoing example has been found in practice to be the most common, it may also happen that the user, instead of dragging and dropping first CUSTOMERS and then ORDERS, might instead drag and drop them in the reverse order, first ORDERS and then CUSTOMERS. The same result is desired, however, namely that an order grid be added to the customer display. Therefore, in similar manner as previously described, the newly-dragged parent finds its already existing children, if any, and the appropriate Master/Detail display is created. In the example of ORDERS and CUSTOMERS, the entry CUSTOMERS.ORDERSGrid would be listed in the Select Grids for this Display Form box 513 in FIG. 5, indicating that an order grid has been added to the customer display. 
     Consider the further example in which a dragged table is both a parent and a child to tables already serving as Root Recordsources per prior drops. For example, DEPARTMENTS may have EMPLOYEES which have ORDERS. DEPARTMENTS and EMPLOYEES are related as parent/child, and EMPLOYEES and ORDERS are related as parent/child. DEPARTMENT and ORDERS might be dragged and dropped in that order, which would not result in the creation of any Master/Detail, since DEPARTMENT and ORDERS are not directly related. If EMPLOYEES is then dragged and dropped, however, the result is to create two Master/Detail displays, an EMPLOYEES detail on DEPARTMENTS and an ORDERS detail on EMPLOYEES. Therefore, within the box 513 in FIG. 5, EMPLOYEES.ORDERSGrid would be displayed, and within the box 511 in FIG. 5, DEPARTMENTS.EMPLOYEESGrid would be displayed. 
     The foregoing discussion has focussed on Master/Detail creation, a crucial part of automating multiple-table application development. A related issue, to be addressed presently, is which forms to create (as nodes in the application diagram), as represented within the display areas 521 and 523 in FIG. 5. Of course, not all tables are part of a Master/Detail relationship. Referring still to FIG. 5, when a table is dragged and dropped, a &#34;freestanding&#34; form containing that table will usually be created. Hence, referring to the frame 520, dragging and dropping CUSTOMERS causes CUSTOMERS to be displayed within the box 521. Furthermore, if the table that was dropped has no parents, a grid will also be created. Hence, CUSTOMERSGrid is displayed within the box 523 in FIG. 5. The underlying rationale is that, if a form is to be accessed directly as opposed to being accessed through another form, it will usually be accessed using Query By Forms (QBF). QBF may be enabled or disabled for each form. If enabled, then the Start-up form will include a QBF icon for that form. Executing the query will result in display of a scrollable grid (e.g., CUSTOMERSGrid) of customers meeting the specified criteria, from which the user may select a particular customer to be displayed (e.g., within the display form CUSTOMER). 
     If ORDERS is later dropped, since ORDERS is a child of CUSTOMER, a Master/Detail form is created. However, if ORDERS is dropped a second time, since a Master/Detail has already been created, a &#34;freestanding&#34; ORDERS Grid form is created, directly accessible through the Start-up form. If ORDERS is dropped yet a third time, then a separate freestanding instance of the ORDERS Grid form is created under another name, for example ORDERPurge. This manner of operation allows forms to be created that are based on existing forms but are for specialized transactions. The transaction-specific form is automatically &#34;wired-into&#34; the other forms in a number of different ways. In the case of ORDERPurge, for example, a transition would be created 1) from ORDER (freestanding) to ORDERPurge (so as to look at an order in a purge way), 2) from the ORDER detail of the CUSTOMER master, 3) directly from the Start-up form, and 4) also in the reverse direction from ORDERPurge to ORDER. These various transitions are reflected on the application drawing and on the property sheets of the various forms, and may be edited by the user. To draw an analogy, the system grows a tree (multiple transitions, including all transitions that the user is likely to want) and then affords the user the opportunity to prune the tree (remove unwanted transitions). The premise therefore is that most often the user will want a particular transition, making it easier to remove the transition in those instances where it is not wanted. 
     As may be appreciated from the foregoing description, the look of the application forms depends on the following conditions: the order in which the tables are dropped; where a table is dropped; and whether the table is related to other tables in the diagram. From the foregoing discussion, one of ordinary skill in the art will appreciate the manner in which, using the present development tool, multiple-table database applications may be created by dragging and dropping Base Tables within the application drawing window. Research has shown, however, that the vast majority of real-world applications are not built upon Base Tables at all, but are based upon QueryDefs and the like, affording the ability to perform database join operations, projections, etc. Whereas detecting relationships from the manipulation of Base Tables is relatively straightforward (given the data model stored in the repository) detecting relationship from the manipulation of QueryDefs is more complicated. In a preferred embodiment, relationships between QueryDefs are inferred in accordance with the following method: 
     1. Determine which tables and which columns within those tables participate in the QueryDefs. 
     2. Determine whether the columns identified in Step 1 include the key fields necessary for the relationship that the respective Base Tables participate in. 
     3. If the answer in Step 2 is yes, then the QueryDefs are caused to &#34;inherit&#34; the relationship from that base table. 
     For example, the user might drag and drop QueryDef1 (DEPARTMENT) followed by QueryDef2 (EMPLOYEES). The system discovers that QueryDef1 includes DEPARTMENT, in particular the Department# field. The system further discovers that QueryDef2 includes EMPLOYEES, and also includes a field corresponding to Department#, say, &#34;myDepartrnent#.&#34; Hence each QueryDef can uphold its half of the underlying relationship between DEPARTMENT and EMPLOYEES. This relationship therefore exists between QueryDef1 and QueryDef2. 
     When the user has defined the application to his or her satisfaction by dragging and dropping tables, QueryDefs, etc., and by modifying their properties as indicated on the accompanying property sheets, the user may then request the system to generate the application. 
     The client-side application will consist of forms, including graphical elements and code pertaining to those graphical elements, and free-standing code that is included in a run-time library and that is not specific to any particular form. The form-specific graphical elements include, for example, menus, toolbars, captions fields, text fields, combo boxes, grids, tab groups, etc. Form-specific code handles events that make the application run, and includes data controls--program constructs that form the link between the target database and the form. Form-specific code is generated from templates, or code modules, that are connected together during generation according to the information stored in the repository, particularly as reflected in FIG. 6, so as to realize the various required forms. A process known as &#34;macro expansion&#34; is performed with respect to the templates (more precisely, copies of the templates) that adapts the templates for a particular use with particular named entities. 
     The main application generation routine proceeds in accordance with the following psuedocode routine: 
     For each Form 
     For each Recordsource 
     generate data control; 
     if Display style from TblDef read in fields and generate caption/text box or combo box onto Form and event code to perform processing; 
     else if Grid style generate Grid; 
     for each Dependent Recordsource of this Recordsource, generate code in reposition event to close/re-open queries of Dependent Recordsources; 
     write to disk; 
     next... 
     With respect to Dependent Recordsources, an example of code generated to close/re-open queries is code to, when a new customer is viewed, obtain that customer&#39;s orders and payments. 
     A list of the available templates in a preferred embodiment of the invention is provided as Appendix II. In general, for each style of form table (e.g., grid, display), a template is provided for each kind of GUI control, for fields within the form table, etc. Executable code is separated from graphics templates to facilitate code reuse. A list of the routines in the run-time library is provided as Appendix III. 
     It will be appreciated by those or ordinary skill in the art that the invention can be embodied in other specific forms without departing from the spirit or essential character thereof. The foregoing description is therefore considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the appended claims, and all changes which come within the meaning and range of equivalents thereof are intended to be embraced therein. 
     
                       APPENDIX I______________________________________Field        Data Type                 Description______________________________________VSVBAppsurrid       Text     Surrid enables support of import                 apps between data-bases (without                 renumbering this row)projectFileName        Text     The name of the project to create                 (name of .vbp file)projectDirectory        Text     Directory for projectFileNametemplateDirectory        Text     Issue: what directory? This is                 presumably the directory itself,                 relative to dbrunTimeDirectory        Text     Where the generic vb code is                 locatedtargetClient Text     any (`vb4`)-later Powerbuilder etc.chgDT        Date/Time                 The last time this app was                 modifiedlastBuildDT  Date/Time                 when last build was rundescription  MemoshowGridCreation        NumberconfirmGridCreation        NumberzoomFactor   NumberisMDIApp     Yes/No   generate App as MDIgenTraceCode Yes/NoVSVBAppFormsappSurrid    Text     Foreign KeyformNum      Number   Starts at 1, supplied by client                 (vb/ab). By convention, the start                 form has number 1.formName     Text     Unique in app. Calc by sys on                 drag; prefix is tblName;                 suffix is grid, qbf, ` ` (display).                 Is `startform` for start form.                 Unalterable after built?formCaption  Text     Defaults to caption of first                 table, with `Grid` appended.                 Empty → formNameformstyle    Text     Example: Start, Grid, Detail,                 MasterDetail. Not user visible                 in R1.numRootsDisplayed        Number   Calc by appSvcsareRootsTabbed        Number   Children means formTables with                 srcFormTable = 0locTop       Number   Within diagram, table&#39;s toplocLeft      NumberlastBuildDT  DatelTimechgDT        Date/Time                 Only reflects change in styledescription  MemolocWidth     Number   Width of form nodelocHeight    Number   Height of form nodeisFormLocked Yes/No   New formTbls/Shows added (with                 isAddedAfterGen flag), but not                 gennedVSVBAppFormTablesappSurrid    Text     Foreign Key - app parentformNum      number   Foreign Key - form parentformTableNum Number   Starts at 1 (root), supplied by clienttblName      Text     or qdefName - goes into data                 Recordsourceprefix       Text     field/table prefix to insure                 uniqueness of names in form.                 AppGen will remove spaces                 to insure valid syntactical                 name.isTableDisplayed        Yes/No   If Table displayed there is no                 menu, otherwise there will be                 menu if FormShow is yesstyle        Text     Grid, Detail, GridDetail                 (of same table)srcFormTableNum        Number   Table that drives this                 (i.e, supplies qry parmValues;                 usually a reln. parent)-                 0 if rootnumChildrenDisplayed        Number   # formTables with                 src = me that are                 displayed; Calc by appSvcsareChildrenTabbed        Yes/No   i.e., use a tab control.                 Followed even if just                 1 child.areChildrenTabbedUser        Yes/No   has user specified tabbed-ness                 (if so, don&#39;t default it)isQBFSupplied        Yes/No   default = 11F(nodeNum = 1 &amp;                 style = any(`grid`, `dboutline`),                 true, false)relnExtSurrid        Text     Via this reln (relnExt)relnIsFromParent        Yes/No   Reln direction is from parentrelnWhereClause        Text     Calculated by systemrelnParms    Text     Parameters for relnWhere.                 Format is parm1 datatype,                 parm2 datatype . . .devWhereClause        Text     Additional Developer selection                 (e. g., `paid` orders)devParms     Text     Parameters for devWhereOrderByClause        Text     Developer-specified order byisBeginTrans Yes/No   Starts/ends a transactionisQueryOverrideable        Yes/No   Can Reln selection be overridden                 by QBFisInitialQBF Yes/No   When not target of Form                 Transition (not usually the case)chgDT        Date/TimelastBuildDT  Date/Time                 When line processed in last build.                 ALERT - we may need to save all                 the values used in the last build,                 so appFixup can use them.description  Memo     Not processed - any notes the                 Developer wants to keep.defaultShowFormTable        Number   formTable for primary showFormNum                   for this formTabledefaultShowFormNum        Number   showFormNum for primary                 showForm for this form TablepickTarget FormNum        Number   Where to go for pick-parent.                 0 → use                 &lt;tblName&gt; &amp; &#34;Grid&#34; for just                 &lt;tblName&gt; if no grid.pickTargetInitialBehavior        Text     any (browse, qbf) is qbf by defaultdoesSourceAffectMe        Yes/No   Does the source form table affect                 me?doIAffectSource        Yes/No   Do I affect the source form table?isAddedAfterGen        Yes/No   Defaults to no, set to yes during                 add-in, or for locked formVSVBAppFormShowsappSurrid    Text     Foreign Key - app parentformShowNum  Number   Starts at onesrcFormNum   Number   Foreigh Key - where show starts                 (Form Number)srcTable Num Number   Foreign Key - where show starts                 (FormTable)targetformNum        Number   Foreign Key - where line ends                 (form Number); assume target                 formTable is always #1isTargetInitialQBF        Yes/NoisShowForm   Yes/No   The &#34;no Thankyou&#34; flag                 (e.g., Don&#39;t show OrderPurge from                 the Outstanding Orders table on                 the Customers/Orders form.)isVisibleAppline        Yes/No   Set means I want appLine (for this                 formShow) visible on the                 application diagram (by default                 &#34;down&#34; is visible,                 &#34;up&#34; is invisible).lastBuildDT  Date/Time                 When last build processedthis                 formShow.chgDT        Date/Timedescription  Memo     Not processed - any notes the                 Developer wants to keep.isAddedAfterGen        Yes/No   Added during add-in, or for                 locked formRelnExtCaption        Text     Caption generated for menu and                 toolbar for formshows______________________________________ 
    
     
                       APPENDIX II______________________________________Templates______________________________________AllShowFormButtonTemplateAllShowFormMenuTemplatePopupCodeTemplateAddButtonCodeTemplateAddUserEventCodeTemplateColCheckBoxCodeTemplateColComboBoxCodeTemplateColMaskedEditCodeTemplateColOLECodeTemplateColOptionButtonCodeTemplateColPictureCodeTemplateColQueryCodeTemplateColTextBoxCodeTemplateColTextBoxMemoCodeTemplateDependentTableCodeTemplateGridCodeTemplateInitCtlCodeTemplateInitCtlDepCodeTemplateInitialDispCodeTemplateInitialDispDepCodeTemplateMainCodeTemplateMenuCommonCodeTemplateResizeCodeTemplateShowFormCodeTemplateShowFormButtonCodeTemplateShowFormSyncCodeTemplateShowFormToolbarCodeTemplateShowFormToolBtnCodeTemplateSSTabCodeTemplateTableTabbedColumnTemplateCheckBoxColumnTemplateComboBoxColumnTemplateMaskedEditColumnTemplateOLEColumnTemplateOptionButtonColumnTemplatePictureColumnTemplateQueryColumnTemplateTextBoxColumnTemplateTextBoxMemoCommandButtonsTemplateDataTemplateDataTemplateGridDataTemplateNoDisplayFormTemplateDependentTablesFormTemplateQueryFormTemplateStartupImagelistImagelistTemplateLightonMDIStartupFormMenuTemplateMenuTemplateExitMenuTemplatePreferencesMenuTemplateQuerymssccprj.sccShowFormMenuTemplateShowFormMenuTemplateSingleTableGroupTemplateRightTableGroupTemplateSiblingsNoTabTableGroupTemplateTopTabbedTableMenuTemplateTableTemplateDisplayTableTemplateGridTableTemplateGridDisplayTableTemplateNoDisplayTableTableTemplatesourceDependentTemplate.vbpToolBarTemplate______________________________________ 
    
     
                       APPENDIX III______________________________________The RUNTIME.BAS module contains all routines called by a VisionBuilder-generated application. RUNTIME.BAS includes functions andsubroutines that provide these services:InitializationRecord ProcessingPick Processing, which allows users to copy a column value froma parent table to the current formError handlingUser interface operations, including menu options and toolbar buttonsUtilities to check (and optionally modify) application statusesA list of these routines follows.______________________________________UTILITY FUNCTIONS AND SUBROUTINES   checkDatFocusChange   displayHelpMsg   displayMsg   endApp   findCodeTableName   getDevParms   getDevWhere   getFrmInstanceMeta   getInternalValuesFromCodeTable   getRelnParms   getRelnWhere   getStartForm   getStoredValuesFromCodeTable   isMDIapp   lastDatWithFocus   setCacheSize   setStatusPanel   showHelp   showInDebugWindow   completeAppInitialization   enableUserDefinedEvent   initGridColCtrls   initializeApp   initializeControls   initializeDatCtrl   initializeStartForm   registerObjNameAsSimilarTo   setDatCtrlMode   setStartFormPICK FUNCTIONS AND SUBROUTINES   processCmdPickClick   registerMyPickForm   setMenuPick   setUpdateInProgress   showPickBtn   unloadPickForm   updateParentFieldsRECORD PROCESSING FUNCTIONS AND SUBROUTINES   allowAddOnAllQDefParentTables   checkAllPending Changes   copyAction   cutAction   decodeValues   deleteCurrent   deleteObjectAction   encodeValues   execUserDefinedEvent   insertObjectAction   pasteAction   pasteSpecialAction   pickOneNum   processCmdPickClick   processKeyDown   processMnuFirstClick   processMnuLastClick   processMnuNextClick   processMnuPreviousClick   registerDependency   repositionAction   retrieve   setDatCtrlMode   setRecordPositionMenu   setUpdateInProgress   syncAllTabDependents   syncRecordSet   syncTargetRecordSet   undoFieldChange   undoRecordChange   unregisterDependency   updateChanges   validateActionUSER INTERFACE FUNCTIONS AND SUBROUTINES   addToolBtn   copyAction   cutAction   deleteObjectAction   disableEditMenu   enableUserDefinedEvent   getMyTargetForm   hideMe   insertObjectAction   pasteAction   pasteSpecialAction   pickOneNum   processKeyDown   registerDependency   setDatCtrlMode   setEditMenu   setMenu   setMenuPick   setRecordStateMenu   setUpdateInProgress   setupQBFToolbar   setupStartupToolbar   setupToolbar   setWindowCaption   showQueryBtn   syncAllTabDependents   undoFieldChange   undoRecordChange   unregisterDependencyERROR HANDLING FUNCTIONS AND SUBROUTINES   dataControlErrorAction   handleDBGridError   showDatabaseError   showError______________________________________