System and method for schema method

• US 7,010,539 B1
• Filed: 09/08/2000
• Issued: 03/07/2006
• Est. Priority Date: 09/08/2000
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Miller, Renee J., Hernandez-Sherrington, Mauricio Antonio, Haas, Laura Myers
• Primary Examiner(s): Gaffin, Jeffrey
• Assistant Examiner(s): Mahmoudi, Hassan
• Application Number:
  US09/658,303
• Time in Patent Office: 2,006 Days
• Field of Search: 707/1, 707/5, 707/3, 707/7, 707/10, 707/104.1, 707/200, 707/103, 707/104, 717/146, 714/143, 714/146
• US Class Current: 707/737
• CPC Class Codes: G06F 16/258 Data format conversion from or to a database
• CPC Class Codes: Y10S 707/99942 Manipulating data structure, e.g. compression, compaction, compilation
• CPC Class Codes: Y10S 707/99945 Object-oriented database structure processing

Abstract

A system and method for generating a source schema-to-target schema mapping includes grouping user-defined value correspondences into potential sets such that, for each potential set, at most one value correspondence per target attribute exists. The value correspondences represent functions and filters for deriving values of target attributes from values of source attributes. Candidate sets are selected from the potential sets and then grouped into ranked covers. Using the best cover, an SQL query representing a source schema-to-target schema mapping is generated.

Claims

1. A computer system, comprising:

a general purpose computer, the computer including logic for undertaking method acts to map data arranged in a source schema into a target schema, the method acts undertaken by the logic including;

receiving at least one value correspondence, each value correspondence representing a function for deriving a value of a target attribute from one or more values of source attributes;

grouping at least some value correspondences into potential sets;

selecting candidate sets from at least some potential sets;

grouping at least some candidate sets into covers; and

using at least one cover, generating at least one query representing a source schema-to-target schema mapping.

2. The computer of claim 1, wherein the method acts undertaken by the logic to execute the grouping act include:

grouping value correspondences into potential sets such that, for each potential set, at most one value correspondence per target attribute exists.

3. The computer of claim 2, wherein the method acts undertaken by the logic further include:

adding a potential set to a set of candidate sets if only one source relation is used to compute mappings using the potential set;

otherwise

adding a potential set to the set of candidate sets only if a join path for the source relations can be identified.

4. The computer of claim 3, wherein the method acts undertaken by the logic further include:

arranging candidate sets into groups such that each group includes every value correspondence at least once, the groups establishing covers.

5. The computer of claim 4, wherein the method acts undertaken by the logic further include:

establishing at least one selected cover;

for each candidate set in the selected cover, creating at least one query; and

combining the queries for the cover.

6. The computer of claim 5, wherein the method acts undertaken by the logic to establish at least one selected cover include:

ranking the covers by at least one of;

a number of candidate sets in each cover, and a number of target attributes; and

presenting ranked covers to a user for selection of one of the covers as the selected cover.

7. The computer of claim 3, wherein the logic undertakes the act of adding a potential set to the set of candidate sets only if a join path for the source relations can be identified using a spanning tree.

8. The computer of claim 1, wherein the logic incrementally undertakes the acts of grouping value correspondences into potential sets, selecting candidate sets, grouping candidate sets into covers, and generating queries representing mappings.

9. A computer-implemented method for generating a mapping from a source schema to a target schema, comprising:

generating a mapping based on at least a subset of value correspondences, each value correspondence representing a function for deriving a value of a target attribute from one or more values of source attributes;

allowing a user, in a user interaction, to incrementally add or delete a value correspondence from the subset;

based on the user interaction, generating a new mapping;

presenting a representation of the new mapping to the user such that the user can view the representation; and

permitting the user to add or delete a value correspondence embodied in the new mapping to generate another mapping.

10. The method of claim 9, wherein the generating act includes:

grouping at least some value correspondences into potential sets;

selecting candidate sets from at least some potential sets;

grouping at least some candidate sets into covers; and

using at least one cover, generating at least one query representing a source schema-to-target schema mapping.

11. The method of claim 10, further comprising:

grouping value correspondences into potential sets such that, for each potential set, at most one value correspondence per target attribute exists.

12. The method of claim 11, further comprising:

adding a potential set to a set of candidate sets if only one source relation is used to compute mappings using the potential set;

otherwise

adding a potential set to the set of candidate sets only if a join path for the source relations can be identified.

13. The method of claim 12, further comprising:

arranging candidate sets into groups such that each group includes every value correspondence at least once, the groups establishing covers.

14. The method of claim 13, further comprising:

establishing at least one selected cover;

for each candidate set in the selected cover, creating at least one query; and

combining the queries for the cover.

15. The method of claim 14, further comprising:

ranking the covers by at least one of;

a number of candidate sets in each cover, and a number of target attributes; and

presenting ranked covers to a user for selection of one of the covers as the selected cover.

16. The method of claim 12, further comprising adding a potential set to the set of candidate sets only, if a join path for the source relations can be identified using a spanning tree.

17. A computer program device comprising:

a computer program storage device readable by a digital processing apparatus; and

a program on the program storage device and including instructions executable by the digital processing apparatus for performing method acts for generating a query representing a source schema-to-target schema mapping, the program comprising;

computer readable code means for establishing plural value correspondences;

computer readable code means for generating subsets of value correspondences such that (1) each subset has at most one value correspondence per target attribute, (2) for each subset requiring more than one source relation to undertake a mapping, a join path can be found between the relations, and (3) each subset includes at least every value correspondence; and

computer readable code means for generating a query using one of the subsets, the query being representative of a source schema-to-target schema mapping.

18. The computer program product of claim 17, further comprising computer readable code means for sorting the subsets and displaying at least portions of a sorted list of subsets, such that a user can establish a selected subset used to generate the query.

19. The computer program product of claim 18, wherein the means for generating subsets generates candidate sets, each subset including one or more candidate sets, and the means for sorting sorts the subsets by inverse number of candidate sets.

20. The computer program product of claim 19, wherein the means for sorting, also sorts the subsets by the number of value correspondences in the subsets.

21. The computer program product of claim 19, wherein the means for generating a query creates at least one query for each candidate set in the selected subset, and then combines the queries for the subset.

22. The computer program product of claim 21, wherein the means for generating subsets and the means for generating a query are incrementally invoked by a user to selectively add or delete value correspondences from a selected subset.