Database-independent mechanism for retrieving relational data as XML

• US 8,447,774 B1
• Filed: 11/18/2005
• Issued: 05/21/2013
• Est. Priority Date: 11/23/2004
• Status: Active Grant

• Current Assignee: Progress Software Corporation
• Original Assignee: Progress Software Corporation
• Inventors: Robie, Jonathan, Coppens, Peter, Van Cappellen, Marc
• Primary Examiner(s): Richardson, James E
• Application Number:
  US11/283,224
• Time in Patent Office: 2,741 Days
• Field of Search: 707/713, 707/716, 707/717, 707/721, 707759-760, 707/764, 707/763, 707/770
• US Class Current: 707/760
• CPC Class Codes: G06F 16/2445 Data retrieval commands; View definitions
• CPC Class Codes: G06F 16/2452 Query translation
• CPC Class Codes: G06F 16/2455 Query execution
• CPC Class Codes: G06F 16/2471 Distributed queries
• CPC Class Codes: G06F 16/8358 Query translation

Abstract

Techniques are disclosed for retrieving both data stored in relational form and data stored in XML form responsive to a single XQuery query. The techniques allow applications to retrieve relational data residing in various relational database management systems by using XQuery and XQuery for Java. In one such embodiment, an embeddable serverless computer component implements the techniques, and includes a combination of one more relational adaptors and a mediator to access relational data and transform it into appropriate XML. The techniques are embeddable, and can be standards-based, database-independent, and operating-system independent. Optimized performance and scalability from desktop to enterprise applications are enabled as the number of users and/or database size increases.

Claims

1. A computer-implemented method for transforming between relational data and XML data, the method comprising:

receiving by a processor an XQuery query from a Java application via an XQuery API for Java (XQJ), the Java application attempting to access a relational data source having a relational data model;

generating by the processor XML results responsive to the XQuery query, based on data from the relational data source by;

processing the XQuery query as specified by a connection-specific option declaration, the connection-specific option declaration providing one or more parameters to control the processing of the XQuery query for a specific connection;

dividing the XQuery query into one or more XQuery expressions;

processing the one or more XQuery expressions as specified by an evaluate-in-memory extension expression, the evaluate-in-memory extension expression specifying a first expression from the one or more XQuery expressions to be evaluated in a memory as XQuery without translating the first expression to structured query language (SQL) for evaluation in the relational data source, the evaluate-in-memory extension expression indicating maximum XQuery conformance when processing the data from the relational data source;

determining for the one or more XQuery expressions if an XML data source or the relational data source is being queried;

retrieving, by an XQuery engine having a first data model incompatible with the relational data model, the relational data if the relational data source is being queried; and

executing in the XQuery engine at least one XQuery expression using the retrieved relational data if the relational data source is being queried; and

sending the XML results to the Java application via the XQJ.

2. The method of claim 1 wherein generating the XML results responsive to the XQuery query further comprises combining results from multiple data sources.

3. The method of claim 1 wherein in response to relational data source queries, generating the XML results comprises:

translating the XQuery query into an SQL query;

querying the relational data source with the SQL query;

receiving one or more SQL query results; and

mapping the one or more SQL query results into XML.

4. The method of claim 1 wherein in response to XML data source queries, generating the XML results comprises:

querying the XML data source with the XQuery query; and

receiving one or more XML XQuery query results.

5. The method of claim 1 further comprising:

combining the XML results generated from multiple sources.

6. The method of claim 1 further comprising:

performing comparisons using value comparison operators.

7. The method of claim 1 further comprising:

caching a number of executed queries for reuse.

8. The method of claim 1 wherein generating the XML results responsive to the XQuery query comprises retrieving both data stored in relational form and data stored in XML form responsive to a single XQuery query.

9. The method of claim 1 wherein the one or more XQuery expressions are processed in parallel to one or more of the XML data source and the relational data source.

10. The method of claim 1 wherein the one or more XQuery expressions are processed in parallel to query the XML data source and the relational data source, indicating that the one or more XQuery expressions querying to the XML data source and the one or more XQuery expressions querying to the relational data source are processed in parallel.

11. The method of claim 1, further comprising:

processing the XQuery query using an XQPreparedExpression to create a prepared query, the XQuery query prepared once and available for multiple executions; and

caching the prepared query in a query pool for reuse.

12. A non-transitory machine-readable storage medium having machine-executable instructions, that when executed by a processor, cause the processor to carry out a process for transforming between relational data and XML data, the process comprising:

receiving an XQuery query from a Java application via an XQuery API for Java (XQJ), the Java application attempting to access a relational data source having a relational data model;

generating XML results responsive to the XQuery query based on data from the relational data source by;

processing the XQuery query as specified by a connection-specific option declaration, the connection-specific option declaration providing one or more parameters to control the processing of the XQuery query for a specific connection;

dividing the XQuery query into one or more XQuery expressions;

processing the one or more XQuery expressions as specified by an evaluate-in-memory extension expression, the evaluate-in-memory extension expression specifying a first expression from the one or more XQuery expressions to be evaluated in a memory as XQuery without translating the first expression to structured query language (SQL) for evaluation in the relational data source, the evaluate-in-memory extension expression indicating maximum XQuery conformance when processing the data from the relational data source;

determining for the one or more XQuery expressions if an XML data source or the relational data source is being queried;

retrieving, by an XQuery engine having a first data model incompatible with the relational data model, the relational data if the relational data source is being queried; and

executing in the XQuery engine at least one XQuery expression using the retrieved relational data if the relational data source is being queried; and

sending the XML results to the Java application via the XQJ.

13. The non-transitory machine-readable storage medium of claim 12 wherein generating the XML results responsive to the XQuery query further comprises combining results from multiple data sources.

14. The non-transitory machine-readable storage medium of claim 12 wherein in response to relational data source queries, generating the XML results comprises:

translating the XQuery query into an SQL query;

querying the relational data source with the SQL query;

receiving one or more SQL query results; and

mapping the one or more SQL query results into XML.

15. The non-transitory machine-readable storage medium of claim 12 wherein in response to XML data source queries, generating the XML results comprises:

querying the XML data source with the XQuery query; and

receiving one or more XML XQuery query results.

16. The non-transitory machine-readable storage medium of claim 12 wherein the process further comprises:

combining the XML results generated from multiple sources.

17. The non-transitory machine-readable storage medium of claim 12 wherein the process further comprises:

performing comparisons using value comparison operators.

18. The non-transitory machine-readable storage medium of claim 12 wherein the process further comprises:

caching a number of executed queries for reuse.

19. The non-transitory machine-readable storage medium of claim 12 wherein generating the XML results responsive to the XQuery query comprises retrieving both data stored in relational form and data stored in XML form responsive to a single XQuery query.

20. The non-transitory machine-readable storage medium of claim 12 wherein the one or more XQuery expressions are processed in parallel to one or more of the XML data source and the relational data source.

21. The non-transitory machine-readable storage medium of claim 12 wherein the one or more XQuery expressions are processed in parallel to query the XML data source and the relational data source, indicating that the one or more XQuery expressions querying to the XML data source and the one or more XQuery expressions querying to the relational data source are processed in parallel.

22. A system for transforming between relational data and XML data, the system comprising:

a processor; and

a machine-readable storage medium having machine-executable instructions, that when executed by the processor, cause the processor to carry out a process for transforming between the relational data and the XML data, the process implementing;

an XQuery interface for receiving an XQuery query from an application attempting to access a relational data source having a relational data model; and

an XQuery engine, the XQuery engine having a first data model incompatible with the relational data model, for generating XML results responsive to the XQuery query based on data from the relational data source by;

processing the XQuery query as specified by a connection-specific option declaration, the connection-specific option declaration providing one or more parameters to control the processing of the XQuery query for a specific connection;

dividing the XQuery query into one or more XQuery expressions;

processing the one or more XQuery expressions as specified by an evaluate-in-memory extension expression, the evaluate-in-memory extension expression specifying a first expression from the one or more XQuery expressions to be evaluated in a memory as XQuery without translating the first expression to structured query language (SQL) for evaluation in the relational data source, the evaluate-in-memory extension expression indicating maximum XQuery conformance when processing the data from the relational data source;

retrieving the relational data if the relational data source is being queried;

executing at least one XQuery expression using the retrieved relational data if the relational data source is being queried; and

sending the XML results to the application via the XQuery interface; and

wherein the XQuery engine includes a mediator module for determining for the one or more XQuery expressions if an XML data source or the relational data source is being queried.

23. The system of claim 22 wherein the XQuery interface is an XQuery API for Java (XQJ) module and the application is a Java application.

24. The system of claim 22 wherein the mediator module is further configured for combining results from multiple data sources.

25. The system of claim 22 wherein the mediator module is further configured to execute the at least one XQuery expression using the retrieved relational data.

26. The system of claim 22 wherein the XQuery engine further includes an SQL adapter for translating a relational data source XQuery query into an SQL query, querying the relational data source with the SQL query, receiving one or more SQL query results, and mapping the one or more SQL query results into XML.

27. The system of claim 26 wherein the XQuery engine further includes an XML adapter for querying the XML data source with an XML data source XQuery query, and receiving one or more XML XQuery query results.

28. The system of claim 22 wherein the system is further configured for combining the XML results generated from multiple sources.

29. The system of claim 22 wherein the system is configured for performing comparisons using value comparison operators.

30. The system of claim 22 wherein the system is configured for caching a number of executed queries for reuse.

31. The system of claim 22 wherein the system is configured for retrieving both data stored in relational form and data stored in XML form responsive to a single XQuery query.

32. The system of claim 22 wherein the one or more XQuery expressions are processed in parallel to one or more of the XML data source and the relational data source.

33. The system of claim 22 wherein the one or more XQuery expressions are processed in parallel to query the XML data source and the relational data source, indicating that the one or more XQuery expressions querying to the XML data source and the one or more XQuery expressions querying to the relational data source are processed in parallel.