Abstract:
The present invention is directed to an improved mapping system and code generation system. Embodiments of the present invention separate the mapping of data elements into two metalevels. The first metalevel maps between types of elements (e.g., string, int, float, varchar, etc.). This first metalevel mapping is associated with an object that contains a method (i.e., a function) which performs the conversion between the type of the element from a first data structure to the type of element in a second data structure. The second metalevel describes the actual mapping between the data elements at issue. Accordingly, the second metalevel results in an instance of the first metalevel object. Source code or scripts generated in accordance with this separation provide numerous advantages including improved flexibility, reduced storage space usage and others. The two metalevel modeling of the invention can be embodied in source code (or script) generators to generate more efficient source code (or scripts).

Description:
FIELD OF THE INVENTION 
     The present invention relates to the mapping of data and, more particularly, a two meta-level modeling approach for mapping typed data and source code generating embodiments employing said two meta-level modeling approach for mapping typed data. 
     BACKGROUND OF THE INVENTION 
     As a result of the ubiquity of computer and information technology, data is often transferred or transmitted between various computer systems (which may or may not be executing on different physical machines). This data may be in the form of messages, objects and the like. As a result of this exchange of information, it is often necessary to map between the data structures (which include objects) of a first system to the data structures of a second system. 
     An example of such transference or transmittal of data occurs when a client-side Java applet (or a server-side servlet) attempts to interact with a database (such as the IBM® DB2® relational database product). The applet may be issuing a request to retrieve data from, or be issuing a request to transfer data to, the database. The data which is to be retrieved or transferred will likely be stored as values associated with a data member (usually referred to as “field” in Java™) in an object which forms part of the applet/servlet. However, data stored in a relational database is stored as a field in a row and column in a table. As a result of the foregoing exemplary interaction, a mapping between the data member in the object and the records in a relational database table is required to ensure that data can be passed between the two systems. 
     Many products have been developed to facilitate the mapping described above. As illustrated in  FIG. 1 , the prior art systems  100  typically provide a graphical user interface (GUI)  112  in which the first data structure  102  and the second data structure  104  are visually rendered. The user is then prompted to visually connect (i.e., map) the elements  106  of the first data structure which are related to the elements  108  of the second data structure  104 . Upon receipt of an instruction (e.g., selecting “Generate” or “OK”, not shown) the prior art systems  100  will generate a script or source code  110 . The source code  110 , when interpreted or compiled and executed, will implement the mapping described by the user input. These prior art mapping systems have often been designed to enable somewhat novice developers to effectively and quickly design applications which implement some business process or logic. 
     While the prior art systems are effective, these systems are not necessarily efficient. For instance, for large systems, there exists the need to map large numbers of elements in first data structures to large numbers of elements in other data structures. As such, under prior art systems known to the inventors, source code is individually generated (or the information is modeled individually and stored in a repository) for each of these large numbers of mappings despite the similarity between many of these mappings. Additionally, when there is a change to one of the data structures (or even to one of the elements in a data structure) then much source code needs to be regenerated. 
     In addition to the preceding shortcomings, prior art systems require the user to be familiar with the data structures of both systems. For example, assume that in the first data structure (an object which forms part of an Enterprise JavaBean) a data element “price” exists. In the second data structure (a relational database table) there exists two columns, “value” and “cost”. Without some additional information (i.e., an understanding of both data structures) a user would have some difficulty in providing the mapping input necessary for the proper source code generation. 
     Finally, present systems often pose difficulties where a second data structure is to be created from a first data structure. These difficulties often arise where there is no direct correlation between the types of elements in the two data structures. Assume, for example, that the first data structure is a Java object and the second data structure is table in a relational database. A data element in the Java object may be of “string” type. Unfortunately, in the relational database there may not exist the “string” type. However, there may be a corresponding type such as the “varchar” type. Unfortunately, without an in-depth understanding of the underlying language of the first data structure (Java, in the example) and the second data structure (SQL, in the example), providing the prior art mapping systems with the input required is very difficult for some users or developers. Unfortunately, it is often novice developers that are often without this understanding. 
     In a further shortcoming of the known present system, it is often the case that some of the functions used to convert are hard coded into these systems and, therefore, hidden from advanced developers. 
     As such, an improved mapping system and code generation which addresses, at least in part, some of the shortcomings identified above would be desired. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an improved mapping system and code generating which addresses, at least in part, some of the various shortcomings described above. 
     Embodiments of the present invention separates the mapping of data elements into two metalevels. The first metalevel maps between types of elements (e.g., string, int, float, varchar, etc.). This first metalevel mapping is associated with an object that contains a method (i.e., a function) which performs the conversion between the type of the element from the first data structure to the type of element in second data structure. 
     The second metalevel describes the actual mapping between the data elements at issue. Accordingly, the second metalevel results in an instance of the first metalevel object (in object oriented embodiments). 
     The two-level model, described herein, allows, in some embodiments, the persistent storage of the type-related portion of the mapping information (e.g., as generated code and, it is expected, more often in some other persistent data model from which code is generated as a separate operation) for all the mappings between objects of the same types. 
     The separation of the mapping into two metalevels provides numerous advantages. 
     First, there may be a significant saving in terms of space required by applications generated which use the mapping. This advantage results from the reuse of the function (or method) which is associated with a particular type-related mapping (e.g., a string to an integer). This type-related function need be only stored once for all mappings between a selected pair of data types rather once for each instance of a mapping between pairs of elements for a selected pair of data types. 
     An additional advantage realized through embodiments of the present invention is increased flexibility. This flexibility is the result of providing a user with the ability to quickly and easily change the function performed for mapping between a first type and a second type. This change is effected by modifying the function in the parent object which models the mapping. This change will then be implicitly applied to all mappings between the first type and the second type. 
     Further flexibility is realized by enabling unique instances of mapping between a given pair of element types (e.g., a “string” to a “varchar”) to be uniquely defined. This advantage is realized by overriding the type mapping function for the given pair of element types with a unique function that will only be applied to the selected mapping of data elements (rather than being applied to all data element mappings for the types associated with the selected pair of element types). 
     In a still further advantage, embodiments of the present invention assist users in mapping between data elements. Assistance may be provided by presenting a the user the type mapping functions available. The mapping types presented to the user may be: for the data type which converts (or transforms) from the data type of the element in the first (or source) data structure; for the data type which converts to the data type of the element of the second (or target) data structure; or for conversion between the data type of the element from first data structure to the data type of the element from the second data structure. 
     In a still further advantage, embodiments of the invention assist developers faced with the situation of using an existing source data structure used by a first system to create a target data structure used by a second system. In this situation, embodiments of the invention may provide developers with a list of functions which convert the data types present in the source data structure to data types which are used by the second system. In this way, developers, who may only have limited knowledge of the second system, are assisted in developing useful interactions between the first and second system. 
     In a still further advantage, embodiments of the present invention may provide for type converters to be explicitly available to a user (usually an advanced user). By providing access to the type converters, advanced users are enabled to customize the information relating to the type converters. 
     Embodiments of the present invention may be employed in source code or script generators which generate source code (or scripts), which when compiled and executed (or interpreted) realize the advantages noted above and others that will be apparent to those of ordinary skill in the art. 
     Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures. 
     In accordance with still another aspect of the present invention there is provided a method for generating source for converting from data stored in a first data element to data stored in a second data element, said first and second data elements associated with a first and second data element types, said method comprising: generating a first source code module to receive said first data element and output said second data element, said first source code module calling a second source code module, said second source code module converting between said first data element type and said second data element type. 
     In accordance with still another aspect of the present invention there is provided a method for converting between from a plurality of first data elements to a plurality of second data elements, each of said plurality of first data elements associated with a first data type and each of said plurality of second data elements associated with a second data type, and wherein a first data element forming part of said plurality of first data elements is to be mapped to a corresponding second data element forming part of said plurality of second data elements said method comprising: generating a first source code module for converting said first data type to said second data type; for each pair of first and second data elements, said first data element of said pair being mapped to said second data element of said pair, generating a second source code module receiving said first data element and outputting said second data element, said second source code module calling said first source code module. 
     In accordance with still another aspect of the present invention there is provided a method for generating source code to convert between a first data element and a second data element, said first data element associated with a first data type and said second data element associated with a second data type, said first and second data elements forming a mapping pair, said method comprising: for data received describing said mapping pair, identifying said first data type and said second data type; generating source code for mapping said first data element to said second data element, said source code calling a data type converter corresponding to the first and second data types identified. 
     In accordance with still another aspect of the present invention there is provided a computer readable media storing instructions and data, said instructions and data for adapting a computer system to for generate source for converting from data stored in a first data element to data stored in a second data element, said first and second data elements associated with a first and second data element types, said computer system adapted to: generate a first source code module to receive said first data element and output said second data element, said first source code module calling a second source code module, said second source code module converting between said first data element type and said second data element type. 
     In accordance with still another aspect of the present invention there is provided a method of source code generation, said source code for mapping a first data object having a first data type to a second data object having a second data type, said method comprising: responsive to input data describing said mapping, generating source code referencing a type converter object, said type converter object converting between said first data type and said second data type. 
     Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the figures which illustrate an example embodiment of this invention: 
         FIG. 1  is a prior art system for generating source code, which when executed, generates source code for converting data from a first data structure to data in a second data structure; 
         FIG. 2  schematically illustrates a computer system embodying aspects of the invention; 
         FIG. 3  schematically illustrates, in greater detail, a portion of the computer system of  FIG. 2 ; 
         FIG. 4  illustrates, in functional block form, a portion of  FIG. 3 ; 
         FIG. 5  illustrates, as a flow chart, the operations performed by the computer system of  FIG. 2 ; 
         FIG. 6  is an example mapping between data elements for which the computer system of  FIG. 2  generates source code; and 
         FIG. 7  is a further example mapping between data elements for which the computer system of  FIG. 2  generates source code. 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment of the invention, computer system  200 , is illustrated in  FIG. 2 . Computer system  200 , illustrated for exemplary purposes as a networked computing device, is in communication with other networked computing devices (not shown) via network  210 . As will be appreciated by those of ordinary skill in the art, network  210  may be embodied using conventional networking technologies and may include one or more of the following: local area networks, wide area networks, intranets, public Internet and the like. Computer system  200  may interact with other networked computer systems (not shown) providing application analysis of a distributed application. 
     Throughout the description herein, an embodiment of the invention is illustrated with aspects of the invention embodied solely on computer system  200 . As will be appreciated by those of ordinary skill in the art, aspects of the invention may be distributed amongst one or more networked computing devices which interact with computer system  200  via one or more data networks such as, for example, network  210 . However, for ease of understanding, aspects of the invention have been embodied in a single computing device—computer system  200 . 
     Computer system  200  includes processing system  202  which communicates with various input devices  204 , output devices  206  and network  210 . Input devices  204 , two of which are shown, may include, for example, a keyboard, a mouse, a scanner, an imaging system (e.g., a camera, etc.) or the like. Similarly, output devices  206  (only one of which is illustrated) may include displays, information display unit printers and the like. Additionally, combination input/output (I/O) devices may also be in communication with processing system  202 . Examples of conventional I/O devices include removable and fixed recordable media (e.g., floppy disk drives, tape drives, CD-ROM drives, DVD-RW drives, etc.), touch screen displays and the like. 
     Exemplary processing system  202  is illustrated in greater detail in  FIG. 3 . As illustrated, processing system  202  includes several components—central processing unit (CPU)  302 , memory  304 , network interface (I/F)  308  and I/O I/F  310 . Each component is in communication with the other components via a suitable communications bus  306  as required. 
     CPU  302  is a processing unit, such as an Intel Pentium™, IBM PowerPC™, Sun Microsystems UltraSparc™ processor or the like, suitable for the operations described herein. As will be appreciated by those of ordinary skill in the art, other embodiments of processing system  202  could use alternative CPUs and may include embodiments in which one or more CPUs are employed. CPU  302  may include various support circuits to enable communication between itself and the other components of processing system  202 . 
     Memory  304  includes both volatile and persistent memory for the storage of: operational instructions for execution by CPU  302 , data registers, application storage and the like. Memory  304  preferably includes a combination of random access memory (RAM), read only memory (ROM) and persistent memory such as that provided by a hard disk drive. 
     Network I/F  308  enables communication between computer system  200  and other network computing devices (not shown) via network  210 . Network I/F  308  may be embodied in one or more conventional communication devices. Examples of a conventional communication device include an Ethernet card, a token ring card, a modem or the like. Network I/F  308  may also enable the retrieval or transmission of instructions for execution by CPU  302  from or to a remote storage media or device via network  210 . 
     I/O I/F  310  enables communication between processing system  202  and the various I/O devices  204 ,  206 . I/O I/F  310  may include, for example, a video card for interfacing with an external display such as output device  206 . Additionally, I/O I/F  310  may enable communication between processing system  202  and a removable media  312 . Although removable media  312  is illustrated as a conventional diskette other removable memory devices such as Zip™ drives, flash cards, CD-ROMs, static memory devices and the like may also be employed. Removable media  312  may be used to provide instructions for execution by CPU  302  or as a removable data storage device. 
     The computer data, instructions and/or applications stored in memory  304  and executed by CPU  302  (thus adapting the operation of computer system  200  as described herein) are illustrated in functional block form in  FIG. 4 . As will be appreciated by those of ordinary skill in the art, the delineation between aspects of the applications illustrated as functional blocks in  FIG. 4  is somewhat arbitrary as the various operations attributed to a particular application as described herein may, in alternative embodiments, be subsumed by another application. 
     As illustrated, for exemplary purposes only, memory  302  stores operating system (OS)  402 , communications suite  404 , integrated development environment  406 , data structures and object repository  408 , source code output  410  and general data storage  412 . 
     OS  402  is an operating system suitable for operation with a selected CPU  302  and the operations described herein. Multitasking, multithreaded OSes such as, for example, IBM AIX™, Microsoft Windows NT™, Linux or the like, are expected in many embodiments to be preferred. OS  402  also includes a Java Virtual Machine (JVM) which is the minimum set of executables, libraries and files that form the Java platform. 
     Communication suite  404  provides, through, interaction with OS  402  and network I/F  308  ( FIG. 3 ), suitable communication protocols to enable communication with other networked computing devices via network  210  ( FIG. 2 ). Communication suite  404  may include one or more of such protocols such as TCP/IP, ethernet, token ring and the like. 
     Integrated development environment (IDE)  406  provides the development environment for users of embodiments of the invention to create applications (e.g., applets, servlets, EJBs, etc.) which require communication between two systems (not shown). As noted above the two systems may be physically resident on the same machine or, alternatively, on separate machines communicating through operation of communication suite  404 . IDE  406  may be embodied in known IDEs, such as IBM WebSphere® Studio, and modified to perform the functions and operations described herein. IDE  406  provides to a user a GUI in which data structures are rendered for visual display on display  204  ( FIG. 2 ). Users of IDE  406  provide mapping input (typically through visually connecting elements in a target and source data structure) and, responsive to the input, IDE  406  outputs source code  410 . 
     As is explained in greater detail below, IDE  406  receives a source and target data structure  102 ,  104  ( FIG. 1 ) and data input by the user (representative of the visual mapping between the elements  106 ,  108  of data structures  102 ,  104 , respectively). Based on the mappings created, the embodiment creates source code  410  (which, in the exemplary embodiment, are objects but could, alternatively include any type of source code or script which are employed to convert a first data element to a second data element) which, when interpreted, perform the requested mapping. 
     Data structures and objects  408  is a repository in which input data structures  106 ,  108  are stored. As mentioned hereinbefore, data structures  106 ,  108  comprise individual data elements (e.g., objects, variables, fields, records, etc.) and may include, for example, relational database tables, objects, structured language data structures and the like. Each individual data structure may include one or more data elements which have an associated type. For example, a data structure which corresponds to metadata describing a relational database table will include data elements which describe the number of columns (e.g., the number of data elements), the type associated with each of those columns (e.g., int, varchar, float, etc.) as well as additional data (e.g., metadata describing any key columns, size of columns, column restrictions, etc.). 
     Also stored in repository  408  are converter objects which have been created by IDE  406 . As described above, the conversion between data elements is separated into two metalevels: the first describes data types; and the second describes a data element of the type described by the first metalevel. Hereinafter, the first metalevel, in the exemplary embodiment, is exemplified by a type converter object (see type converter object  610  of  FIG. 6 ) while the second is exemplified by a data element converter object. 
     Type converter objects represent the first or top metalevel which provide the conversion function to map between data types (e.g., from “string” to “int”). As is explained in greater detail, there will generally exist only one type converter object in repository  408  for a conversion between a first data element type and a second data element type. That is, for converting between from a “string” (as that type has been defined by the language of the first system—e.g., Java) to an “int” (as that type has been defined by the language of the second system—e.g., SQL), there will, in many situations, be a single type converter object stored in repository  408  which is generated by IDE  406  and which performs this desired conversion. A second type converter object, also created by IDE  406  and stored in repository  408 , would be tasked with performing conversion between a second pair of data element types (e.g., from “string” to “float”, for example). As will be apparent, additional type converter objects would be created and stored in repository  408  for each additional pair of data types. As persons of ordinary skill in the art will appreciate, a data type, “int” for example, may be defined differently amongst different systems. As such, type converter objects are created to convert from a specific data type to another specific data type. For example, one system may define a “float” has having a certain level of precision (e.g., 32 bits) while another system defines “float” with a different level of precision (e.g., 64 bits). In such a situation, different type converter objects may be created for converting between from the first “float” definition and other type converter objects for converting from the second “float” definition. 
     As indicated above, data element converter objects are also created by the exemplary embodiment. Data element converter objects are also stored in repository  408 . 
     Source code  410 , as mentioned above, is code generated by IDE  406  so as to implement the mappings between data elements  106  and  108  ( FIG. 1 ), as input by the developer. In an alternative embodiment, source code  410  may also be output to, and stored by, repository  408   
     The source code generated by IDE  406  will be better understood with reference to the pseudo-code (which is in Java) which is included below. As will be appreciated by those of ordinary skill in the art the invention is not limited to Java but could equally be embodied using other languages such as C++, C# (from Microsoft Corporation), SmallTalk, as well as structured languages. 
     The pseudo code implemented below includes three classes: Mapping; TypeMapping; and TypeConverter. With reference to the pseudo-code the following entities are used:
         t 1  is a first data type (e.g., a type associated with a first data element  106  illustrated in  FIG. 1 )   t 2  is a second data type (e.g., a type associated with a second data element  108  illustrated in  FIG. 1 )   d 1  is a first data element or data object (e.g., first data element  106 )   d 2  is a second data element or data object (e.g., first data element  106 )   dm 1  is the data representative of the mapping input by the user into IDE  406     tc 1  is a type converter object (e.g., a type converter object that is forms part of the source code output  410  and may be stored by repository  408 )       

     Referring to the pseudo-code below for the Mapping class, objects instantiated from the Mapping class receive the first and second data elements (or objects) for which the conversion is desired. That is, a Mapping object will be created to convert from a first data element  106  (FIG.  1 )—e.g., d 1 —to a second data element  108 .—e.g., d 2 . It is to be noted that Mapping objects do not, in most instances, include a type converter. However, as is explained in greater detail below, in some specific instances, such as those instances when a user implements a type converter that is unique to a selected pair of data elements, a mapping object may include a type converter. 
     
       
         
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
           
               
                   
               
               
                 MAPPING CLASS 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 public class Mapping 
               
               
                   
                 { 
               
             
          
           
               
                   
                 private DataObject input; 
               
               
                   
                 private DataObject output; 
               
               
                   
                 private TypeConverter converter; 
               
               
                   
                 private TypeMapping typeMapping; 
               
               
                   
                 ... 
               
               
                   
                 public TypeMapping getTypeMapping( ) { 
               
             
          
           
               
                   
                 return typeMapping; 
               
             
          
           
               
                   
                 } 
               
               
                   
                 public setTypeMapping(TypeMapping tm) { 
               
             
          
           
               
                   
                 typeMapping = tm; 
               
             
          
           
               
                   
                 } 
               
               
                   
                 public getConverter( ) { 
               
             
          
           
               
                   
                 if (converter != null) return converter; 
               
               
                   
                 else return typeMapping.getConverter( ); 
               
             
          
           
               
                   
                 } 
               
               
                   
                 public setConverter(TypeConverter c) { 
               
             
          
           
               
                   
                 typeMapping = c; 
               
             
          
           
               
                   
                 } 
               
             
          
           
               
                   
                 } 
               
               
                   
                   
               
             
          
         
       
     
     As shown in the pseudo-code below, objects instantiated from the TypeMapping class are designed to receive as input the data types associated with the first and second data elements (e.g., t 1  and t 2 , respectively). 
     
       
         
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
           
               
                   
               
               
                 TYPEMAPPING CLASS 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 public class TypeMapping 
               
               
                   
                 { 
               
             
          
           
               
                   
                 private MetaObject input; 
               
               
                   
                 private MetaObject output; 
               
               
                   
                 private TypeConverter converter; 
               
               
                   
                 ... 
               
               
                   
                 public getConverter( ) { 
               
             
          
           
               
                   
                 return converter; 
               
             
          
           
               
                   
                 } 
               
               
                   
                 public setConverter(TypeConverter c) { 
               
             
          
           
               
                   
                 typeMapping = c; 
               
             
          
           
               
                   
                 } 
               
             
          
           
               
                   
                 } 
               
               
                   
                   
               
             
          
         
       
     
     As shown in the pseudo-code below, objects instantiated from the TypeConverter class are design with a single method, a method which converts from an input type to an output type. The string Output2InputFunction would, in an alternative embodiment, be used to convert data in the opposite direction. The Output2InputFunction would provide support bi-directional data flow. As such, the Input2OutputFunction and the Output2InputFunction would enable tracking of the function needed to convert from the input to the output type as well as the reverse function for converting the output type to the input type. 
     
       
         
               
             
               
               
             
               
               
             
               
               
             
               
               
             
               
               
             
           
               
                   
               
               
                 TYPECONVERTER CLASS 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 public class TypeConverter 
               
               
                   
                 { 
               
             
          
           
               
                   
                 private String input2OutputFunction; 
               
               
                   
                 private String ouput2InputFunction; 
               
               
                   
                 ... 
               
               
                   
                 public String setInput2OutputFunction( ) { 
               
             
          
           
               
                   
                 return input2OuputFunction; 
               
             
          
           
               
                   
                 } 
               
             
          
           
               
                   
                 } 
               
               
                   
                   
               
             
          
         
       
     
     Referencing operations  500  ( FIG. 5 ) which are performed by computer system  200  ( FIG. 2 ) and more particularly the data and instructions stored in memory  300  which form IDE  406 , source code  410  (which in the exemplary embodiment is in the Java language) will be generated by IDE  406  which will enable a user&#39;s mapping of a first data element  106  (d 1 ) to a second data element  108  (d 2 ). Initially, a user provides mapping data (which may be input through a GUI) between two elements, d 1  and d 2 , respectively (S 502 ). The mapping data, dm 1 , can be codified by instantiating an object of the Mapping class as indicated in the following pseudo-code:
         Mapping dm 1 =new Mapping(d 1 , d 2 );       

     It should be noted that dm 1  does not include a specific type converter. 
     System  200  then ascertains the data types associated with the data elements—t 1  and t 2  (S 504 ). 
     Once the types associated with the d 1  and d 2  have been ascertained, an object of class TypeMapping—the object being identified as “tm 1 ”—is instantiated (if one does not already exist— 506 ) using types t 1  and t 2  ( 508 ). Also, an type converter object, tc 1 , is instantiated (if one does not already exist— 506 ) from the TypeConverter Class using the data types associated with d 1  and d 2 . The tc 1  object is then used to set typeMapping element of the tm 1  object. As will be appreciated, a converter specific to the two data types, t 1  and t 2 , is now associated with the tm 1  object. The instantiation of tm 1  and tc 1  and the setting of the converter in object tm 1  is illustrated in the pseudo-code directly below.
         TypeMapping tm 1 =new TypeMapping(t 1 , t 2 );   TypeConverter tc 1 =new TypeConverter(“convertToT 2 ”, “convertToT 1 ”));   tm 1 .setConverter(tc 1 );       

     In the exemplary embodiment, the type converter objects are created in advance of a data mapping and stored in repository  408 . That is, for the most part, type converter objects are predefined and the type mapping instances are created by IDE  406 . However, in alternative embodiments, mechanisms that allow users to define additional type mappings of their own can also be employed. 
     If a conversion between a first type, t 1 , and a second type, t 2 , is not known by the system then a user may be prompted to input data describing the conversion to be performed. However, in most instances, it is expected that a previously created type converter object (stored in repository  408 , for example) would exist. But, as described below, embodiments of the present invention enable users to override the function defined by a (previously created) type converter object, if this need arises. In most cases, however, it is expected that the predefined type converter objects will be employed and a user will not have to be concerned about this functionality. The visual mapping input provided by the user through operation of IDE  406  will automatically “connect” the mapping data to the appropriate type converter object. 
     Once TypeConverter and TypeMapping objects have been instantiated for converting between the selected pair of data types, the setTypeMapping method of dm 1  is invoked as indicated by the following pseudo-code ( 510 ):
         m 1 .setTypeMapping(tm 1 );       

     Based on the objects created, when a type converter for data mapping dm 1  is required it can be obtained, as indicated, using the following pseudo-code:
         TypeConverter tc=dm 1 .getConverter( );       

     This will return tc 1 , the type converter from the associated type mapping tm 1 . 
     From the foregoing, persons of ordinary skill in the art will appreciate the numerous benefits and advantages of the above described embodiment of the present invention including, for example, reduced source code size, the ability to quickly and easily change a single converter function (e.g., tc) for a pair of data types which is then applied to all conversions involving the pair of data types, as well as others. 
     In addition to the foregoing, many alternatives and enhancements of the present invention are possible. 
     For example, it may be desirable in certain instances for a user to override the default type mapping function associated with a pair of data types. This is illustrated in  FIG. 7  where the default type is indicated by default type mapping function  710  and a unique mapping function  710  is attached to a specific and selected pair of data elements. 
     A user may effect a specific type converter (“myconverter”) by providing additional input into the GUI of IDE  406  (by, perhaps, using a right mouse button click on the connector visually connecting the selected pair of data elements). This input will invoke the following pseudo-code:
         tc.setInput2OutputFunction(“myConverter”);       

     In the exemplary embodiment, underlying notification listeners in IDE  406  will result in the following pseudo-code be executed:
         copyOftc=clone(tc);   copyOfTc.setInput2OutputFunction(“myConverter”);   tm 1 .setConverter(copyOfTc);       

     That is, a user&#39;s modification of a default converter type results in a copy or clone of the original type converter object, tc, being created for the selected pair of data elements only. This cloned object is then modified based on the user&#39;s input. 
     In a further alternative, the present invention may be embodied so as to assist developers in providing input data. In the above and main example, mapping object, dm 1 , was provided by the user as a result of an explicit mapping between two data elements (or objects). However, as indicated hereinbefore, a user may not be able to provide such mapping for numerous reasons including confusion. Accordingly, based on a selection of a single data element, system  200  may suggest an appropriate mapping based on the type converter objects previously created. For example, a user may have selected a first data element, t 1 , which is of type float. And, for the user, there exists two possible second data elements, t 2  and t 2 ′, which are of type int and string, respectively. System  200  may present to the user a list of available type converter objects which convert from the type of the selected first element. Based on this additional information the user may then be able to provide a selection of a second data element. Continuing with the example above, the user may be presented with information indicating that a converter only exists from a float type to a string type. Accordingly, based on this additional information a user may select t 2 ′ as this data element is of type string. This feature of the embodiment could also be applied in reverse (e.g., the user selects the second data element but requires assistance to select the first data element). 
     As will be appreciated by those skilled in the art, modifications to the above-described embodiment can be made without departing from the essence of the invention. For example, an embodiment of the invention could be applied to assist in the mapping of extensible markup language (XML) schema types. 
     In a further embodiment of the present invention, the two-level model, described hereinbefore, could also be employed so that the type-related portion of the mapping information for all the mappings between objects of the same types (e.g., type converters) are persistently stored in a repository (e.g., a database). In this embodiment, mapping code (e.g., mapping objects) could be generated as a separate operation which reference the type-related data in the repository. 
     In a still further embodiment of the present invention, intelligent automatic matching (requiring little or no user input) could also being achieved. In this embodiment, previously stored type mapping information (e.g., type converters stored in a repository) combined with name matching techniques, could be employed so that mappings can be deduced entirely without user interaction. 
     While one (or more) embodiment(s) of this invention has been illustrated in the accompanying drawings and described above, it will be evident to those skilled in the art that changes and modifications may be made therein without departing from the essence of this invention. All such modifications or variations are believed to be within the sphere and scope of the invention as defined by the claims appended hereto. Other modifications will be apparent to those skilled in the art and, therefore, the invention is defined in the claims.