Data processing

• US 20030055805A1
• Filed: 01/02/2001
• Published: 03/20/2003
• Est. Priority Date: 02/11/2000
• Status: Active Grant

• Current Assignee: Observatory House Windsor Road
• Original Assignee: Observatory House Windsor Road
• Inventors: Gardner, Paul Anton Richardson
• Granted Patent: US 6,725,242 B2
• Time in Patent Office: Days
• US Class Current: 707/1
• CPC Class Codes: G06F 16/2322 using timestamps
• CPC Class Codes: G06F 16/2329 using versioning
• CPC Class Codes: G06F 16/2477 Temporal data queries
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99954 Version management

Abstract

A data processor comprises a number of databases for storing records and a plurality of user systems capable of accessing the databases. The user systems each include a datastore/application environment instance with which users can interface. Host systems may include more than one instance. The datastores contain time-versioned views of records. The data processor is operable in at least two modes, a normal operation mode in which an evaluation in response to a user enquiry can be carried out using records relevant to a current viewpoint time and time span, and a recovery operation mode in which records relevant to a viewpoint time and time span for a previous evaluation are accessed and used to exactly reproduce the previous evaluation.

Claims

1. Data processing apparatus comprising one or more databases for storing respective pluralities of records and a plurality of user systems capable of accessing the one or more databases, wherein the user systems each comprise a respective datastore/application environment instance with which users may interface, wherein the datastores contain time-versioned views of records, wherein the data processing apparatus is operable in at least two modes, a normal operation mode in which records relevant to a current viewpoint time and time span are accessed and employed in an evaluation in response to a user enquiry, and a recovery operation mode in which records relevant to a viewpoint time and time span for a previous evaluation are accessed and employed to reproduce exactly the previous evaluation, and wherein the time-versioned views of records each include

(a) at least one attribute;

(b) a time span indicating the time span for which the attribute is valid;

(c) a creation time indicating when the record was created, and

(d) a type field indicating whether the record is a concrete record, or a delta record that possibly modifies the attribute value of a previous concrete or delta record.

2. Data processing apparatus as claimed in claim 1, wherein each datastore instance is allocated a respective identity which is stored in the records pertaining thereto.

3. Data processing apparatus as claimed in claim 1, wherein the datastore instances are object store instances, and wherein each object store instance contains time-versioned views of records of objects stored in rows of a table and keyed by respective object identities.

4. Data processing apparatus as claimed in claim 3, wherein the sole or most recent concrete record for a said object has an end time of “

top”

, corresponding to a hypothetical maximum time, and has no delta record corresponding to any part of its time span, which sole or most recent concrete record is the only record used for locking.

5. Data processing apparatus as claimed in claim 3, wherein the records further include a version information field in which is a marker indicating the version of the object that the record was created for.

6. Data processing apparatus as claimed in claim 5, wherein the version information field includes another marker indicating the number of records belonging to the respective version of the object, and wherein the version information field includes the creation time for the most recent version of the object.

7. Data processing apparatus as claimed in claim 5, wherein the existence of a delta record corresponding to any part of the time span of a said concrete record, is indicated by a further marker in the said concrete record.

8. Data processing apparatus as claimed in claim 6, wherein the object store instances also store their records in a respective one of the databases, wherein in the case of non-synchronisation of object store instances clocks and clock-skew between object store instances, the creation time of the most recent version of an object is employed in a calculation to determine if time adjustment is required or if an evaluation should be rerun.

9. Data processing apparatus as claimed in claim 1, wherein there is a third mode of operation, comprising a speculative mode, in which an evaluation is made with arbitrary time values in order to determine the result of an evaluation which would have occurred at the corresponding point in time.

10. Data processing apparatus as claimed in claim 1, wherein there is a fourth mode of operation, comprising a review mode, in which the impact of a change to the parameters used in an evaluation is determined.

11. Data processing apparatus as claimed in claim 3, wherein to support recovery the most recently used viewpoint time and time span, together with a commit time, are stored as an instance of a session object, the session object being linked to an object identifying the object store/application environment instance involved and added to a relevant atomic unit.

12. A data processing method comprising storing respective pluralities of records in one or more databases, and permitting a user to access the one or more databases by means of a respective one of a plurality of user systems, each comprising a respective datastore/application environment instance with which users may interface, the datastores containing time-versioned views of records, wherein there are at least two modes for data processing, a normal mode in which records relevant to a current viewpoint time and time span are accessed and employed in an evaluation in response to a user enquiry, and a recovery mode in which records relevant to a viewpoint time and time span for a previous evaluation are accessed and employed to reproduce exactly the previous evaluation, and wherein the time-versioned views of the records each include

(a) at least one attribute;

(b) a time span indicating the time span for which the attribute is valid;

(c) a creation time indicating when the record was created, and

(d) a type field indicating whether the record is a concrete record, or a delta record that possibly modifies the attribute value of a previous concrete or delta record.

13. A method as claimed in claim 12, wherein each datastore instance is allocated a respective identity which is stored in the records pertaining thereto.

14. A method as claimed in claim 12, wherein the datastore instances are object store instances, and wherein each object store instance contains time-versioned views of records of objects stored in rows of a table and keyed by respective object identities.

15. A method as claimed in claim 14, wherein the sole or most recent concrete record for a said object has an end time of “

top”

, corresponding to a hypothetical maximum time, and has no delta record corresponding to any part of its time span, and wherein said sole or most recent concrete record is the only record used for locking.

16. A method as claimed in claim 14, wherein the records further include a version information field, and wherein the method includes the step of inserting a marker indicating the version of the object that the record was created for into the version information field.

17. A method as claimed in claim 16, including the step of inserting another marker, indicating the number of records belonging to the respective version of the object, into the version information field, and including the step of inserting into the version information field the creation time for the most recent version of the object.

18. A method as claimed in claim 16, and including the step of indicating the existence of a delta record, corresponding to any part of the time span of a said concrete record, by a further marker in the said concrete record.

19. A method as claimed in claim 17, including the step of storing the object store instances records in a respective one of the databases, and, in the case of non-synchronisation of object store instances clocks and clock-skew between object store instances, employing the creation time of the most recent version of an object in a calculation to determine if time adjustment is required or if an evaluation should be rerun.

20. A method as claimed in claim 12, and including a third mode for data processing, the third mode comprising a speculative mode in which an evaluation is made with arbitrary time values in order to determine the result of an evaluation which would have occurred at the corresponding point in time.

21. A method as claimed in claim 12, and including a fourth mode for data processing, the fourth mode comprising a review mode in which the impact of a change to the parameters used in an evaluation is determined.

22. l A method as claimed in claim 14, wherein to support recovery, including the step of storing the most recently used viewpoint time and time span, together with a commit time, as an instance of a session object, the session object being linked to an object identifying the object store/application environment instance involved, and including the step of adding the session object to a relevant atomic unit.

23. An information carrier holding a program for performing a data processing method, the method comprising storing respective pluralities of records in one or more databases, and permitting a user to access the one or more databases by means of a respective one of a plurality of user systems, each comprising a respective datastore/application environment instance with which users may interface, the datastores containing time-versioned views of records, wherein there are at least two modes for data processing, a normal mode in which records relevant to a current viewpoint time and time span are accessed and employed in an evaluation in response to a user enquiry, and a recovery mode in which records relevant to a viewpoint time and a time span for a previous evaluation are accessed and employed to reproduce exactly the previous evaluation, and wherein the time-versioned view of records each include

(a) at least one attribute;

(b) a time span indicating the time span for which the attribute is valid;

(c) a creation time indicating when the record was created, and

(d) a type field indicating whether the record is a concrete record, or a delta record that possibly modifies the attribute value of a previous concrete or delta record.