Viewing a temporal database as a collection of time-referenced (or timestamped) facts, a time reference in such a database is called relative if its value is dependent of the context. For example, this context can be the current time, now, or it can be another instant.
The relationship between times can be qualitative (before, after, etc.) as well as quantitative (3 days before, 397 years after, etc.). If quantitative, the relationship is specified using a time span.
Examples: “Mary’s salary was raised yesterday,” “it happened sometime last week,” “it happened within 3 days of Easter, 2005” “the Jurassic is sometime after the Triassic,” and “the French revolution occurred 397 years after the discovery of America”.
The simplest example of a relative timestamp is a period that starts at a time in the past and extends to now, such as (2005, now). As the clock ticks, this period gets longer.
- 1.Jensen CS, Dyreson CE. A consensus glossary of temporal database concepts – February 1998 version. In: Etzion O, Jajodia S, Sripada S, editors. Temporal databases: research and practice. Berlin: Springer; 1998. p. 367–405. LNCS, vol. 1399.Google Scholar