Integrating relational databases in an object oriented environment

• US 5,937,409 A
• Filed: 07/25/1997
• Issued: 08/10/1999
• Est. Priority Date: 07/25/1997
• Status: Expired due to Term

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle Corporation
• Inventors: Wetherbee, Jonathan
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): Mizrahi, Diane D.
• Application Number:
  US08/901,738
• Time in Patent Office: 746 Days
• Field of Search: 707/2, 707/8, 707/9, 707/10, 707/102, 707/201, 707/204, 707/501, 707/1, 707/103, 711/112, 345/333, 345/339, 345/356, 348/7, 395/683
• US Class Current: 1/1
• CPC Class Codes: G06F 16/289 Object oriented databases
• CPC Class Codes: Y10S 707/99931 Database or file accessing
• CPC Class Codes: Y10S 707/99932 Access augmentation or optimizing
• CPC Class Codes: Y10S 707/99944 Object-oriented database structure

Abstract

A relational mapper supports the storage of objects from an object oriented environment in one or more relational databases. The relational mapper generates tables in a relational data store for abstract class types, and it generates a mapping, in any predetermined relationship, to map at least one member of an object to a table for the class type in the relational data store. The relational mapper maps members of a class type to members of a data source. A storage type map is generated to map the data source members of the data source to columns of the relational database table for the class type. The relational mapper is bidirectional such that the relational mapper maps data from a relational database to create objects in accordance with a type system of an object oriented environment. The relational mapper generates metadata to describe the object such that the object, created from the relational database, is a full fledged object of the object oriented system.

Claims

1. A method of storing an object in a relational database, said method comprising the steps of:

selecting at least one class type from an object oriented software system for storage in a table of a relational database, wherein said class type is defined in accordance with a type system of said object oriented software system that includes at least one type system member;

generating class type mapping information, as metadata, to map said class type to a logical relational database table comprising at least one column; and

generating member mapping information, as metadata, to map said at least one type system member of said class type to said at least one column of said logical relational database table corresponding to said class type, wherein said mapping information is independent of an implementation of said class type and independent of an implementation of a relational database.

2. The method as set forth in claim 1, further comprising the steps of:

generating mapping tables, for use in said object oriented system, to describe said mapping between said at least one type system member of said class type to said relational database table for said class type;

generating a relational database table from said logical relational database table; and

storing objects, instantiated from said class type, in said relational table in accordance with said mapping tables.

3. The method as set forth in claim 1, wherein the step of generating mapping information comprises the steps of:

generating a relational type map object for each class type to specify a mapping for a class type to a relational database table; and

generating a relational member map object for each type system member of a class type to specify a mapping of a type system member to a corresponding relational database table.

4. The method as set forth in claim 1, wherein the step of generating a logical relational table comprises the step of:

generating a table object for each logical relational table; and

generating at least one column object for each table object to describe columns of said logical relational table.

5. The method as set forth in claim 1, further comprising the steps of storing said mapping information in a physical repository such that said mapping information persists in a data store accessible to said object oriented system.

6. The method as set forth in claim 1, further comprising the steps of generating a logical relational table to support a plurality of class types derived from a single class hierarchy.

7. The method as set forth in claim 1, wherein the step of generating mapping information to map said at least one type system member of said class type to at least one column of said logical relational database table comprises the step of mapping at least one attribute on an interface supported by said class type to a column of said logical relational table that corresponds to said class type.

8. The method as set forth in claim 7, wherein the step of mapping at least one attribute on an interface comprises the step of mapping scalar and complex scalar attributes on an interface supported by said class type to a column of said logical relational table that corresponds to said class type.

9. The method as set forth in claim 7, wherein the step of mapping at least one attribute on an interface comprises the step of mapping a collection of class types to a logical relational table that corresponds to said class type of said collection referenced.

10. The method as set forth in claim 1, wherein the steps of generating mapping information comprises the steps of:

generating class type members, wherein each class type member comprises a type;

defining type system members on said class type as class type members; and

mapping said class type members to columns of said logical relational table for said class type.

11. The method as set forth in claim 10, wherein the step of mapping said class type members comprises the step of mapping a private attribute of a class type, not exposed by an interface supported by said class type, to a class type member.

12. The method as set forth in claim 10, further comprises the steps of:

providing a means to generate an association to associate at least two interfaces supported by a least one class type; and

providing, through said class type members, a means to constrain an association to specific class types that support said interface of said association.

13. The method as set forth in claim 1, wherein the steps of generating mapping information comprises the step of generating at least one data source for said class type, wherein said data source comprises data source members and defines a data structure to store instances of said class type in accordance with a particular implementation of said class type.

14. The method as set forth in claim 13, further comprising the steps of generating, after modification of a class type, a second data source for said class type that includes data source members that support modification of said class type, wherein objects instantiated from said class type subsequent to modification are supported by said second data source, and objects instantiated from said class type prior to modification are supported by an original data source so that data sources supports legacy objects.

15. The method as set forth in claim 13, wherein the step of mapping members of a class type to said archive members in said archive comprises the step of mapping multiple members of a class type to a single archive member.

16. A method for integrating at least one table of a relational database into in an object oriented system, said method comprising the steps of:

storing metadata to describe at least one class type and interface registered with said object oriented system;

analyzing metadata for a schema of objects;

mapping a table from said relational database to a class type and interface based on said metadata; and

generating class type and interface definitions for said table in accordance with said mapping, such that said class type and interface definitions permit instantiation of full fledged objects in said object oriented system from tables in said relational database.

17. The method as set forth in claim 16, wherein the step of generating class type and interface definitions comprises the step of generating metadata to describe said class type and interface definitions.

18. The method as set forth in claim 16, wherein the step of mapping tables to class type and interface definitions comprises the step of mapping at least one column of a table to an attribute on an interface supported by a class type.

19. A computer readable medium comprising a set of instructions stored therein, which when executed by a computer, causes the computer to perform the steps of:

selecting at least one class type from an object oriented software system for storage in a table of a relational database, wherein said class type is defined in accordance with a type system of said object oriented software system that includes at least one type system member;

generating class type mapping information, as metadata, to map said class type to a logical relational database table comprising at least one column; and

generating member mapping information, as metadata, to map said at least one type system member of said class type to said at least one column of said logical relational database table corresponding to said class type, wherein said mapping information is independent of an implementation of said class type and independent of an implementation of a relational database.

20. The computer readable medium as set forth in claim 19, further comprising instructions for:

generating mapping tables, for use in said object oriented system, to describe said mapping between said at least one type system member of said class type to said relational database table for said class type;

generating a relational database table from said logical relational database table; and

storing objects, instantiated from said class type, in said relational table in accordance with said mapping tables.

21. The computer readable medium as set forth in claim 19, wherein instructions for generating mapping information comprise instructions for:

generating a relational type map object for each class type to specify a mapping for a class type to a relational database table; and

generating a relational member map object for each type system member of a class type to specify a mapping of a type system member to a corresponding relational database table.

22. The computer readable medium as set forth in claim 19, wherein the instructions for generating a logical relational table comprise instructions for:

generating a table object for each logical relational table; and

generating at least one column object for each table object to describe columns of said logical relational table.

23. The computer readable medium as set forth in claim 19, further comprising instructions for storing said mapping information in a physical repository such that said mapping information persists in a data store accessible to said object oriented system.

24. The computer readable medium as set forth in claim 19, further comprising instructions for generating a logical relational table to support a plurality of class types derived from a single class hierarchy.

25. The computer readable medium as set forth in claim 19, wherein instructions for generating mapping information to map said at least one type system member of said class type to at least one column of said logical relational database table comprise instructions for mapping at least one attribute on an interface supported by said class type to a column of said logical relational table that corresponds to said class type.

26. The computer readable medium as set forth in claim 25, wherein instructions for mapping at least one attribute on an interface comprise instructions for mapping scalar and complex scalar attributes on an interface supported by said class type to a column of said logical relational table that corresponds to said class type.

27. The computer readable medium as set forth in claim 25, wherein instructions for mapping at least one attribute on an interface comprise instructions for mapping a collection of class types to a logical relational table that corresponds to said class type of said collection referenced.

28. The computer readable medium as set forth in claim 19, wherein instructions for generating mapping information comprise instructions for:

generating class type members, wherein each class type member comprises a type;

defining type system members on said class type as class type members; and

mapping said class type members to columns of said logical relational table for said class type.

29. The computer readable medium as set forth in claim 28, wherein instructions for mapping said class type members comprise instructions for mapping a private attribute of a class type, not exposed by an interface supported by said class type, to a class type member.

30. The computer readable medium as set forth in claim 28, further comprising instructions for:

providing a means to generate an association to associate at least two interfaces supported by a least one class type; and

providing, through said class type members, a means to provide an association to specific class types that support said interface of said association.

31. The computer readable medium as set forth in claim 19, wherein the instructions for generating mapping information comprise instructions for generating at least one data source for said class type, wherein said data source comprises data source members and defines a data structure to store instances of said class type in accordance with a particular implementation of said class type.

32. The computer readable medium as set forth in claim 31, further comprising instructions for generating, after modification of a class type, a second data source for said class type that includes data source members that support modification of said class type, wherein objects instantiated from said class type subsequent to modification are supported by said second data source, and objects instantiated from said class type prior to modification are supported by an original data source so that data sources supports legacy objects.

33. The computer readable medium as set forth in claim 31, wherein the instructions for mapping members of a class type to said archive members in said archive comprise instructions for mapping multiple members of a class type to a single archive member.

34. A computer readable medium comprising a set of instructions stored therein, which when executed by a computer, causes the computer to perform the steps of:

storing metadata to describe all class types registered with said object oriented system;

analyzing metadata for a schema of objects;

mapping a table from said relational database to a class type and interface based on said metadata; and

generating class type and interface definitions for said table in accordance with said mapping, such that said class type and interface definitions permit instantiation of full fledged objects in said object oriented system from tables in said relational database.

35. The computer readable medium as set forth in claim 34, wherein instructions for generating class type and interface definitions comprise instructions for generating metadata to describe said class type and interface definitions.

36. The computer readable medium as set forth in claim 34, wherein instructions for mapping tables to class type and interface definitions comprise instructions for mapping at least one column of a table to an attribute o n a n interface supported by a class type.