Timeslice Operator

Synonyms

Rollback operator; State query

Definition

The valid-timeslice operator may be applied to any temporal relation that captures valid time. Given also a valid-time element as a parameter, it returns the argument relation reduced in the valid-time dimension to just those time(s) specified by the valid-time element. The transaction timeslice operator is defined similarly, with the exception that the argument relation must capture transaction time.

Key Points

Several types of timeslice operators are possible. Some may restrict the time parameter to intervals or instants. Some operators may, given an instant parameter, return a conventional relation or a transaction-time relation when applied to a valid-time or a bitemporal relation, respectively; other operators may always return a result relation of the same type as the argument relation.

Oracle supports timeslicing through its flashback queries. Such queries can retrieve all the versions of a row between two transaction times (a...