Object conversion method from a flat object space to a class structured space

• US 5,732,257 A
• Filed: 09/13/1995
• Issued: 03/24/1998
• Est. Priority Date: 09/13/1995
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Company (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Constant, Steve J., Atkinson, Toni
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): Corrielus, Jean M.
• Application Number:
  US08/527,644
• Time in Patent Office: 923 Days
• Field of Search: 395/604, 395/613, 395/614, 395/682, 395/683, 395/707
• US Class Current: 1/1
• CPC Class Codes: G06F 16/258 Data format conversion from or to a database
• CPC Class Codes: G06F 16/289 Object oriented databases
• CPC Class Codes: G06F 8/51 Source to source
• CPC Class Codes: G06F 9/4488 Object-oriented
• CPC Class Codes: Y10S 707/99934 Query formulation, input preparation, or translation
• CPC Class Codes: Y10S 707/99943 Generating database or data structure, e.g. via user interface

Abstract

An object conversion system which allows applications and their data to migrate from a classless object space to a class-based object space independently of other applications and data. A set of procedures operate upon, update, and maintain a set of four tables, including, (1) a field location table for use in determining whether a field was created by a classless object model application or a class-based object model application; (2) a field method table for storing mappings from fields to both their corresponding class and method for access; (3) an identification table for storing the mapping between a classless object ID and its corresponding class-based object ID; and (4) an object description table for storing the mapping between a classless object ID to every field associated with that classless object ID. The procedures which operate upon these tables include (1) field creation means for creating a field; (2) field retrieval means for retrieving the value of a field; (3) field setting means for setting the value of a field; (4) object field retrieval means for retrieving the values of every field for a given classless object ID; (5) proxy object creation means for creating a classless object ID for a newly-created local class-based object; (6) proxy object deletion means for removing the classless object ID for a deleted or migrated class-based object; and (7) object location means for locating the classless object IDs for all objects having a given value for a given field.

Claims

1. An object conversion system for allowing coexistence of data and applications based on a classless object model with data and applications based on a class-based object model, wherein a classless object based on said classless object model comprises at least a classless object identifier and a plurality of fields having field values, and wherein a class-based object based on said class-based object model comprises a class-based object identifier, a plurality of attributes, and a plurality of methods for accessing said attributes, according to a defined class, said object conversion system comprising:

a field location table for storing a mapping designation for indicating whether a field of a classless object has been mapped to an attribute of a class-based object;

a field method table for storing mappings of fields to both their corresponding class and attribute;

an identification table for storing mappings between a classless object identifier and its corresponding class and class-based object identifier;

an object description table for storing mappings between a classless object identifier to each of said plurality of fields associated with said classless object identifier; and

a plurality of procedures comprising field creation means for creating a field;

field retrieval means for retrieving the value of a field;

field setting means for setting the value of a field;

object field retrieval means for retrieving the values of every field associated with a given classless object identifier;

proxy object creation means for creating a classless object identifier for a newly-created class-based object;

proxy object deletion means for removing the classless object identifier of a deleted class-based object; and

object location means for locating the classless object identifiers for all classless objects having a given value for a given field.

2. The system of claim 1, wherein said field location table comprises a plurality of entries, each entry comprising:

a field identifier, and

a designation indicating whether or not the field associated with said field identifier has been mapped to an attribute of a class.

3. The system of claim 1, wherein said field method table comprises a plurality entries, each entry comprising:

a field identifier, and

an attribute to which a field referenced by said field identifier is mapped.

4. The system of claim 1, wherein said field method table comprises a plurality of entries, each entry comprising:

a field identifier,

a method for accessing the attribute to which a field referenced by said field identifier is mapped,

a method type designating what type of operation said method performs, and

a class to which said attribute belongs.

5. The system of claim 1, wherein said identification table comprises a plurality of entries, each entry comprising:

a class-based object identifier for referencing a class-based object,

a class to which said class-based object belongs, and

a classless object identifier for referencing a classless object having a field which maps to an attribute of said class-based object.

6. The system of claim 1, wherein said object description table comprises a plurality of entries, each entry comprising:

a classless object identifier for referencing a classless object, and

a list of every field associated with said classless object.

7. The system of claim 6, wherein said list of every field associated with said classless object comprises a linked list.

8. The system of claim 1, wherein said field creation means includes processing means for performing the steps of:

accepting as input an input field identifier for referencing a field and an input attribute to which said referenced field is mapped;

creating a new entry in the field location table, said entry comprising said input field identifier and a designation indicating said referenced field is created by an application based on said class-based object model; and

,

creating a new entry in the field method table, said entry comprising said input field identifier, and said input attribute to which said referenced field is mapped.

9. The system of claim 1, wherein said field creation means includes processing means for performing the steps of:

accepting as input an input field identifier for referencing a field and an input method for accessing an attribute to which said referenced field is mapped, an input method type designating the operation performed by said method, and an input class to which said attribute belongs;

creating a new entry in the field location table, said entry comprising said input field identifier and a designation indicating said referenced field is created by an application based on said class-based object model; and

,

creating a new entry in the field method table, said entry comprising said input field identifier, and said input method, said input method type, and said input class.

10. The system of claim 1, wherein said field retrieval means includes processing means for performing the steps of:

accepting as input an input classless object identifier and an input field_-- identifier for referencing a field from which to retrieve its value;

performing a lookup on the field location table to determine whether said referenced field has been mapped; and

where said referenced field has not been mapped,

performing a lookup on a classless object referenced by said input classless object identifier to retrieve the value of said referenced field; and

where said referenced field has been mapped,

performing a lookup, based on said input classless object identifier, on the identification table to retrieve a corresponding class-based object identifier for said input classless object identifier,

performing a lookup, based on said input field identifier, on the field method table to determine a corresponding class and corresponding attribute to which said referenced field is mapped, and

performing a lookup on a class-based object referenced by said corresponding class-based object identifier, said referenced class-based object belonging to said corresponding class and having said corresponding attribute, to retrieve the value of said corresponding attribute to which said referenced field is mapped.

11. The system of claim 1, wherein said field retrieval means includes processing means for performing the steps of:

accepting as input an input classless object identifier and an input field identifier for referencing a field from which to retrieve its value;

performing a lookup on the field location table to determine whether said referenced field has been mapped; and

where said referenced field has not been mapped,

performing a lookup on a classless object referenced by said input classless object identifier to retrieve the value of said referenced field; and

where said referenced field has been mapped,

performing a lookup, based on said input classless object identifier, on the identification table to retrieve a corresponding class-based object identifier for said input classless object identifier,

performing a lookup, based on said input field identifier, on the field method table to determine a corresponding class and corresponding method for retrieving a corresponding attribute to which said referenced field is mapped, and

performing a method call on a class-based object referenced by said class-based object identifier, said referenced class-based object belonging to said corresponding class and having said corresponding attribute, to retrieve the value of said corresponding attribute to which said referenced field is mapped.

12. The system of claim 1, wherein said field setting means includes processing means for performing the steps of:

accepting as input an input field value, an input classless object identifier and an input field identifier for referencing a field to which said input field value is to be set;

performing a lookup on the field location table to determine whether said referenced field has been mapped; and

where said referenced field has not been mapped,

performing a lookup on a classless object referenced by said input classless object identifier to set the value of said referenced field to the input field value; and

where said referenced field has been mapped,

performing a lookup, based on said input classless object identifier, on the identification table to retrieve a corresponding class-based object identifier for said input classless object identifier,

performing a lookup, based on said input field identifier, on the field method table to determine a corresponding class and corresponding attribute to which said referenced field is mapped, and

performing a lookup on a class-based object referenced by said corresponding class-based object identifier, said referenced class-based object belonging to said corresponding class and having said corresponding attribute, to set the value of said corresponding attribute to which said referenced field (220 is mapped to the input field value.

13. The system of claim 1, wherein said field setting means includes processing means for performing the steps of:

accepting as input an input field value, an input classless object identifier and an input field identifier for referencing a field to which said input field value is to be set;

performing a lookup on the field location table to determine whether said referenced field has been mapped; and

where said referenced field has not been mapped,

performing a lookup on a classless object referenced by said input classless object identifier and said input field identifier to set the value of said referenced field; and

where said referenced field has been mapped,

performing a lookup, based on said input classless object identifier, on the identification table to retrieve a corresponding class-based object identifier for said input classless object identifier,

performing a lookup, based on said input field identifier, on the field method table to determine a corresponding class and corresponding method for retrieving the value of a corresponding attribute to which said referenced field is mapped, and

performing a method call on a class-based object referenced by said class-based object identifier, said referenced class-based object belonging to said corresponding class and having said corresponding attribute, to set the value of said corresponding attribute to which said referenced field is mapped to the input field value.

14. The system of claim 1, wherein said object field retrieval means includes processing means for performing the steps of:

accepting as input a classless object identifier for referencing a classless object;

performing a lookup on the object description table to obtain a list of every field associated with said referenced classless object, each field being referenced by its corresponding field identifier; and

for each field in said list, performing the steps of;

performing a lookup on the field location table to determine whether or not said referenced field has been mapped; and

where said referenced field has not been mapped,

retrieving the value of said referenced field from said referenced classless object; and

where said referenced field has been mapped,

performing a lookup on the field method table to obtain a corresponding class and corresponding attribute to which said referenced field is mapped,

performing a lookup on the identification table to obtain a corresponding class-based object identifier for referencing a corresponding class-based object to which said referenced classless object corresponds, and

performing a lookup on said corresponding class-based object, said referenced class-based object belonging to said corresponding class and having said corresponding attribute, to retrieve the value of said corresponding attribute to which said referenced field is mapped.

15. The system of claim 1, wherein said object field retrieval means includes processing means for performing the steps of:

accepting as input a classless object identifier for referencing a classless object;

performing a lookup on the object description table to obtain a list of every field associated with said referenced classless object, each field being referenced by its corresponding field identifier; and

for each field in said list, performing the steps of;

performing a lookup on the field location table to determine whether or not said referenced field has been mapped; and

where said referenced field has not been mapped,

retrieving the value of said referenced field from said referenced classless object; and

where said referenced field has been mapped,

performing a lookup on the field method table to obtain a corresponding class and corresponding method for accessing the corresponding attribute to which said referenced field is mapped,

performing a lookup on the identification table to obtain a corresponding class-based object identifier for referencing a corresponding class-based object to which said referenced classless object corresponds, and

performing a method call on said corresponding class-based object, said referenced class-based object belonging to said corresponding class and having said corresponding attribute, to retrieve the value of said corresponding attribute to which said referenced field is mapped.

16. The system of claim 1, wherein said object field retrieval means includes processing means for performing the steps of:

accepting as input a classless object identifier for referencing a classless object;

performing a lookup on the object description table to obtain a list of every field associated with said referenced classless object, each field being referenced by its corresponding field identifier; and

for each field in said list, utilizing the field retrieval means 122 to retrieve the value of each field associated with said referenced classless object and contained in said list.

17. The system of claim 1, wherein said proxy object creation means includes processing means for performing the steps of:

accepting as input an input class-based object identifier for referencing a class-based object, an input class to which said referenced class-based object belongs, and a list of every field associated with said referenced class-based object;

creating a new classless object identifier for use by applications based on said classless object model; and

adding an entry into the identification table, said entry comprising said newly created classless object identifier, said input class-based object identifier, and said input class; and

adding an entry into the object description table, said entry comprising said newly created classless object identifier and said input list of fields.

18. The system of claim 1, wherein said proxy object deletion means includes processing means for performing the steps of:

accepting as input a class-based object identifier; and

removing all entries in the identification table referenced by said input class-based object identifier; and

removing all entries in the object description table referenced by said input class-based object identifier.

19. The system of claim 1, wherein said object location means includes processing means for performing the steps of:

accepting as input an input field identifier for referencing a field and an input field value;

performing a lookup on the field location table to determine whether said referenced field has been mapped; and

where said referenced field has not been mapped,

sorting through a classless object database comprising a plurality of classless objects to locate each classless object owning said referenced field;

comparing the value of said referenced field of said field owning classless object to said input field value;

retrieving and returning the classless object identifier referencing said field owning classless object where said value of said referenced field equals the input field value; and

where said referenced field has been mapped,

performing a lookup, based on said input field identifier, on the field method table to determine a corresponding class and corresponding attribute to which said referenced field is mapped,

performing a lookup, based on said corresponding class, on the identification table to retrieve a class member list comprising a plurality of class-based object identifiers and referencing each class-based object belonging to said corresponding class, and

for each of said plurality of class-based object identifiers contained in said class member list, performing a lookup on its corresponding class-based object to retrieve the value of said corresponding attribute to which said referenced field is mapped, comparing the value of said corresponding attribute to said input field value, and creating a class-based object identifier list of all class-based object identifiers having a corresponding attribute value equal to the input field value, wherein said referenced field is mapped to said attribute; and

performing a lookup on the identification table to retrieve and return a classless object identifier for each class-based identifier contained in said class-based identifier list.

20. The system of claim 1, wherein said object location means includes processing means for performing the steps of:

accepting as input an input field identifier for referencing a field and an input field value;

performing a lookup on the field location table to determine whether said referenced field has been mapped; and

where said referenced field has not been mapped,

sorting through a classless object database comprising a plurality of classless objects to locate each classless object owning said referenced field;

comparing the value of said referenced field of said field owning classless object to said input field value;

retrieving and returning the classless object identifier referencing said field owning classless object where said value of said referenced field equals the input field value; and

where said referenced field has been mapped,

performing a lookup, based on said input field identifier, on the field method table to determine a corresponding class and corresponding method for accessing a corresponding attribute to which said referenced field is mapped,

performing a lookup, based on said corresponding class, on the identification table to retrieve a class member list comprising a plurality of class-based object identifiers and referencing each class-based object belonging to said corresponding class, and

for each of said plurality of class-based object identifiers contained in said class member list, performing a method call on its corresponding class-based object to retrieve the value of said corresponding attribute to which said referenced field is mapped, comparing the value of said corresponding attribute to said input field value, and creating a class-based object identifier list of all class-based object identifiers having a corresponding attribute value equal to the input field value, wherein said referenced field is mapped to said attribute; and

performing a lookup on the identification table to retrieve and return a classless object identifier for each class-based identifier contained in said class-based identifier list.

21. The system of claim 1, further comprising migrating means for migrating classless objects based on said classless object model to class-based objects based on said class-based object model.

22. The system of claim 21, said migrating means accepting as input an input mapping file comprising a plurality of entries, each entry comprising a field identifier for referencing a field and a corresponding class and attribute to which said field is mapped, and said migrating means also accepting as input a plurality of classless objects owned by a migrating application, wherein each of said plurality of owned classless objects comprises a classless object identifier and a plurality of fields having field values and referenced by field identifiers, said migrating means processing a single classless object one at a time from said plurality of input classless objects by reference to its classless object identifier, and for each field owned by said single classless object and having its corresponding field identifier contained in said input mapping file, performing the steps of:

adding an entry to the field location table, said field location table entry comprising the field identifier referencing said owned field and a designation indicating that said field has been mapped;

adding an entry to the field method table, said field method table entry comprising the field identifier for referencing said owned field, and the class and attribute contained in the input mapping file to which said owned field is mapped;

creating a new class-based object identifier;

adding an entry to the identification table, said identification table entry comprising the classless object identifier referencing the single classless object, the class contained in the input mapping file to which the owned field is mapped, and the newly created class-based object identifier;

instantiating a new class-based object, corresponding to the newly created class-based object identifier, by setting the attribute to which the owned field is mapped to the value of the owned field; and

unsetting the value of the owned field of the single classless object.

23. The system of claim 21, said migrating means accepting as input an input mapping file comprising a plurality of entries, each entry comprising a field identifier for referencing a field and a corresponding class, attribute, and method for accessing said attribute to which said field is mapped, and said migrating means also accepting as input a plurality of classless objects owned by a migrating application, wherein each of said plurality of owned classless objects comprises a classless object identifier and a plurality of fields having field values and referenced by field identifiers, said migrating means processing a single classless object one at a time from said plurality of input classless objects by reference to its classless object identifier, and for each field owned by said single classless object and having its corresponding field identifier contained in said input mapping file, performing the steps of:

adding an entry to the field location table, said field location table entry comprising the field identifier referencing said owned field and a designation indicating that said field has been mapped;

adding an entry to the field method table, said field method table entry comprising the field identifier for referencing said owned field, and the class and method for accessing the attribute to which said owned field is mapped;

creating a new class-based object identifier;

adding an entry to the identification table, said identification table entry comprising the classless object identifier referencing the single classless object, the class contained in the input mapping file to which the owned field is mapped, and the newly created class-based object identifier;

instantiating a new class-based object, corresponding to the newly created class-based object identifier, by setting the attribute to which the owned field is mapped to the value of the owned field; and

unsetting the value of the owned field of the single classless object.

24. An object migration system for migrating data and applications from a classless object model platform to a class-based object model platform, wherein a classless object based on said classless object model comprises at least a classless object identifier and a plurality of fields having field values, and wherein a class-based object based on said class-based object model comprises a class-based object identifier, a plurality of attributes and a plurality of methods according to a defined class, said object migration system comprising:

a field location table for storing a mapping designation for indicating whether a field of a classless object has been mapped to an attribute of a class-based object;

a field method table for storing mappings between fields and their corresponding classes and methods for accessing their corresponding attributes;

an identification table for storing mappings between a classless object identifier and its corresponding class and class-based object identifier;

an object description table for storing mappings between a classless object identifier to each of said plurality of fields associated with said classless object identifier; and

migration means for migrating classless objects based on said classless object model to class-based objects based on said class-based object model, and for updating said field location table, field method table, and identification table for allowing access to said migrated classless objects by non-migrated applications based on the classless object model.

25. The system of claim 24, said migrating means accepting as input an input mapping file comprising a plurality of entries, each entry comprising a field identifier for referencing a field and a corresponding class, attribute, and method for accessing said attribute to which said field is mapped, and said migrating means also accepting as input a plurality of classless objects owned by a migrating application, wherein each of said plurality of classless objects comprises a classless object identifier and a plurality of fields having field values and referenced by field identifiers, said migrating means processing a single classless object one at a time from said plurality of input classless objects by reference to its classless object identifier, and for each field owned by said single classless object and having its corresponding field identifier contained in said input mapping file, performing the steps of:

adding an entry to the field location table, said field location table entry comprising the field identifier referencing said owned field and a designation indicating that said field has been mapped;

adding an entry to the field method table, said field method table entry comprising the field identifier for referencing said owned field, and the class and method for accessing the attribute to which said owned field is mapped;

creating a new class-based object identifier;

adding an entry to the identification table, said identification table entry comprising the classless object identifier referencing the single classless object, the class contained in the input mapping file to which the owned field is mapped, and the newly created class-based object identifier;

instantiating a new class-based object, corresponding to the newly created class-based object identifier, by setting the attribute to which the owned field is mapped to the value of the owned field; and

unsetting the value of the owned field of the single classless object.