Editing Temporal database (section)

==Bitemporal modelling==
{{Main article|Bitemporal modeling}}
A [[bitemporal model]] contains both valid and transaction time. This provides both ''historical'' and ''rollback'' information. Historical information (e.g.: "Where did John live in 1992?") is provided by the valid time. Rollback (e.g.: "In 1992, where did the database believe John lived?") is provided by the transaction time. The answers to these example questions may not be the same{{snd}} the database may have been altered since 1992, causing the queries to produce different results.

The valid time and transaction time do not have to be the same for a single fact. For example, consider a temporal database storing data about the 18th century. The valid time of these facts is somewhere between 1701 and 1800. The transaction time would show when the facts were inserted into the database (for example 1998-01-21).