1. Temporal DBMS JD Pack Software Architecture

2. Introduction • Conventional databases store “now” data • Can store huge amounts of data, but only data in the present • What about systems that might require past and even future data storage? (banking, inventory, geographical, medical) • Temporal DBMS • Databases designed to handle time-dependent data • Supported using temporal data models, temporal SQL • Key aspects: valid time, transaction time

3. Valid Time • Period of time which data is considered to be valid • Storing historical data • Retrieve data later, rather than overwrite with new information • Data can be valid as past, present, or future • Unknown time values are marked as ∞ http://www.timeconsult.com/TemporalData/TemporalDB.html

4. Transaction Time • Time period which data is considered to be true • Only occurs in past or present data • Allows DBMS to be presented as states • Temporal SQL can be used to pull data within a specified time frame that shows when the data was asserted • Useful for taxes or auditing Name City ValidStartValidEndT.StartT.End John Doe, Smallville, 3-Apr-1975, ∞, 4-Apr-1975, 27-Dec-1994 John Doe, Smallville, 3-Apr-1975, 26-Aug-1994, 27-Dec-1994, ∞ John Doe, Bigtown, 26-Aug-1994, ∞, 27-Dec-1994, 2-Feb-2001 John Doe, Bigtown, 26-Aug-1994, 1-Jun-1995, 2-Feb-2001, ∞ John Doe, Beachy, 1-Jun-1995, 3-Sep-2000, 2-Feb-2001, ∞ John Doe, Bigtown, 3-Sep-2000, ∞, 2-Feb-2001, 1-Apr-2001 John Doe, Bigtown, 3-Sep-2000, 1-Apr-2001, 1-Apr-2001, ∞

5. Bitemporal Relations • Relationship between Valid & Transaction Time • Provides both historical and rollback data • Storing data using this method allows access to snapshots of the database http://www.timeconsult.com/TemporalData/snapshot.gif

6. Current Temporal Implementations • Oracle Workspace Manager • TimeDB • PostgreSQL • Teradata • Anchor Modeling • IBM DB2 • OSIsoft (PI System)

7. Limitations • Schema Evolution • It is vital that data be stored using the schema version in which it originally appeared • The smallest of changes to the history of a value have to be redone by hand for each version of the schema • Time standards • SQL2 standards are poorly designed and suffer from range limitations and efficiency • Inconsistency • Lack of coherent architectures, commercialization • Performance

8. Example – MediaWiki Schema Wiki Commons

9. Sources • http://temporal.projects.pgfoundry.org/reference.html • https://cs.arizona.edu/~rts/pubs/LNCS639.pdf • http://www.timeconsult.com/TemporalData/TemporalDB.html • http://www.cs.arizona.edu/people/rts/tdbbook.pdf • http://www.mediawiki.org/wiki/Manual:Database_layout