Application time; Business time Data time; Intrinsic time; Logical time; Real-world time
The valid time of a fact is the time when the fact is true in the modeled reality. Any subset of the time domain may be associated with a fact as its valid time. Thus, valid timestamps may be sets of time instants and time intervals, with single instants and intervals being important special cases. Valid times are usually supplied by users.
While other temporal aspects have been proposed, such as “decision time” and “event time,” closer analysis indicates that the decision and event time of a fact can be captured as either a valid time or a transaction time of some related fact.
For example, consider a valid-time Faculty table with attributes Name and Position (i.e., either Assistant Professor, Associate Professor, or Professor) that captures the positions of faculty members. The valid time then captures when a faculty member held a specific position.
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