Virtualizing objects within queries

• US 7,917,547 B2
• Filed: 06/10/2008
• Issued: 03/29/2011
• Est. Priority Date: 06/10/2008
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Hughes, Gregory L., Olenick, Brad M., Kerer, Clemens
• Primary Examiner(s): CHEN, TE Y
• Application Number:
  US12/136,616
• Publication Number:
  US 20090307192A1
• Time in Patent Office: 1,022 Days
• Field of Search: None
• US Class Current: 707/804
• CPC Class Codes: G06F 16/289 Object oriented databases

Abstract

The present invention extends to methods, systems, and computer program products for virtualizing objects within queries. Embodiments of the invention virtualize data access for use with queries. Virtualization can be implemented within any portion of a syntax tree. For example, data can be virtualized for a property of an object that is itself another object. Data virtualization facilitates lazy evaluation of query expressions. That is, actual property values for properties within a data construction statement are virtualized until a query specifically requests the actual property values. Further, data virtualization also conserves resources and results in more efficient query evaluations.

Claims

1. A method, implemented within a computer system that includes one or more processors and memory storing instructions which, when executed by the one or more processors implement the method, for creating a data provider that virtualizes data access to an object so that a subset of a plurality of properties of the object are accessible without constructing the entire object, the method comprising:

an act of a computer system that includes one or more processors receiving a data construction statement that describes at least a portion of a syntax tree of an object having a plurality of properties, wherein the value of at least one of the plurality of properties is determinable by execution of a query expression, and wherein the data construction statement includes;

an indication of a type of object that the data construction statement represents a construction of;

one or more property identifiers, wherein each property identifier identifies a property of the object; and

one or more mappings, wherein each mapping maps a property identifier to a corresponding query expression, and wherein the corresponding query expression indicates how to compute a value for the property of the object identified by the corresponding property identifier; and

an act of the computer system creating a data provider in response to receiving the data construction statement, wherein the data provider virtualizes data access to the object and facilitates lazy evaluation of queries on the object by creating a partial construction of the object based on the data construction statement, wherein the partial construction of the object provides access to values of one or more properties of the object by executing one or more query expressions corresponding to the one or more properties of the object without having to evaluate the entire data construction statement or fully construct the entire object, and wherein the data provider includes;

a reference to the data construction statement, wherein the reference transitively includes references to the type, the property identifiers, and the corresponding mappings of the data construction statement.

2. The method as recited in claim 1, wherein the act of receiving a data construction statement comprises an act of receiving user input submitting the data construction statement for evaluation prior to the submission of any queries against properties of the virtualized object described by the data construction statement.

3. The method as recited in claim 1, wherein the act of receiving a data construction statement comprises an act of receiving the data construction statement from an existing data provider, the data construction statement being contained within a query expression from the property mappings of the existing data provider.

4. The method as recited in claim 1, further comprising:

an act of receiving a request from a data consumer for the value of a property within the data provider;

an act of referring to the corresponding one or more mappings to locate a query expression corresponding to the identified property;

an act of evaluating the query expression to obtain a property value for the property; and

an act of the returning the property value to data consumer.

5. The method as recited in claim 4, wherein the act of evaluating the query expression to obtain a property value for the property comprises an act of evaluating the query expression to obtain the actual property value for the property.

6. The method as recited in claim 5, wherein the act of evaluating the query expression to obtain the actual property value for the property comprises an act of referring to a data repository.

7. The method as recited in claim 6, wherein the act of referring to a data repository comprises an act of referring to the data repository to access data for calculating the actual property value without accessing data for calculating the values of any other properties described by the data construction statement.

8. The method as recited in claim 4, wherein the an act of evaluating the query expression to obtain a property value for the property comprises an act of evaluating the query expression to obtain a further data provider, and wherein the further data provider virtualizes the property value from the data provider.

9. The method as recited in claim 8, wherein the act of evaluating the query expression to obtain a further data provider comprises an act of evaluating a further data construction statement contained in the data provider to create the further data provider.

10. The method as recited in claim 1, further comprising:

an act of receiving a property value access query, the property value access query including a property identifier from the data construction statement;

an act of identifying the initial data provider for responding to the property value access query based on the property identifier;

an act of placing the initial data provider in a known location associated with the query evaluator;

an act of creating a data consumer for the property value access query;

an act of the data consumer accessing the initial data provider from the known location;

an act of the data consumer requesting the property value of the identified property from the initial data provider;

an act of the initial data provider looking up a query expression corresponding to the identified property from the previously received data construction statement;

an act of evaluating the query expression to obtain a property value for the property;

an act of the initial data provider returning the obtained property value to the data consumer;

an act of the data consumer receiving the obtained property value; and

an act of the data consumer placing the received property value in the known location for further processing.

11. The method as recited in claim 10, wherein the act of evaluating the query expression to obtain a property value for the property comprises an act of accessing data from a database.

12. The method as recited in claim 10, wherein the act of evaluating the query expression to obtain a property value for the property comprises an act of constructing a further data provider.

13. A method implemented within a computer system that includes a processor and memory storing instructions which, when executed by the processor implement the method for responding to a query using a query evaluator that utilizes a data provider to virtualize data access to an object so that a subset of a plurality of properties of the object are accessible to the query evaluator without constructing the entire object, the method comprising:

an act of a computer system that includes one or more processors receiving a property value access query, wherein the property value access query queries for a property value of a property identified in a previously received data construction statement that describes at least a portion of a syntax tree of an object having a plurality of properties, and wherein the value of at least one of the plurality of properties is determinable by execution of a query expression;

an act of the computer system identifying a data provider created from the previously received data construction statement based on data contained in the property value access query, wherein the data provider virtualizes data access to the object and facilitates lazy evaluation of queries on the object by creating a partial construction of the object based on the data construction statement, wherein the partial construction of the object provides access to values of one or more properties of the object by executing one or more query expressions corresponding to the one or more properties without having to evaluate the entire data construction statement or fully construct the entire object;

an act of the computer system placing the identified data provider in a known location associated with the query evaluator;

an act of the computer system creating a data consumer for the property value access query;

an act of the data consumer accessing the identified data provider from the known location;

an act of the data consumer requesting the property value of the identified property from the data provider;

an act of the data consumer receiving the property value of the identified property from the data provider;

an act of the data consumer placing the received property value in the known location for further processing.

14. The method as recited in claim 13, wherein the act of the data consumer receiving the property value of the identified property from the data provider comprises an act of the data consumer receiving the actual property value of the property from the data provider.

15. The method as recited in claim 13, wherein the act of receiving the actual property value of the property from the data provider comprises an act of receiving the actual property value of the property without having to evaluate query expressions for other properties described by the previously received data construction statement.

16. The method as recited in claim 13, wherein the act of the data consumer receiving the property value of the identified property from the data provider comprises an act of the data consumer receiving a further data provider from the data provider, and wherein the further data provider virtualizes the property value from the data provider.

17. The method as recited in claim 13, wherein the act of the data consumer placing the received property value in the known location for further processing comprises an act of the data consumer placing the actual property value of the property in the known location.

18. The method as recited in claim 13, wherein the act of the data consumer placing the obtained property value in the known location for further processing comprises an act of placing a further data provider in the known location, and wherein the further data provider virtualizes the property value from the data provider.

19. The method as recited in claim 18, further comprising:

an act of creating a further data consumer for the property value access query;

an act of the further data consumer accessing the further data provider from the known location;

an act of the further data consumer requesting the property value of the identified property from the further data provider;

an act of the data consumer receiving the property value of the identified property from the data further provider;

an act of the data consumer placing the received property value in the known location for further processing.

20. The method as recited in claim 19, wherein the act of receiving the property value of the property comprises an act of receiving the actual property value of the property without having refer to a data repository to evaluate query expressions for properties described by the previously received data construction statement and without having to evaluate query expressions for other properties described by the further data construction statement.