Valid-time indeterminacy

Abstract

In valid-time indeterminacy, it is known that an event stored in a temporal database did in fact occur, but it is not known exactly when the event occurred. An extension of the tuple-timestamped temporal data model, called the possible chronons data model, is presented to support valid-time indeterminacy. In the possible chronons data model, each event is represented with a set of possible chronons, delimiting when the event might have occurred and a probability distribution over the set. The TQuel query language is extended using constructs that specify the user's credibility in the underlying valid-time data and the user's plausibility in the relationships among that data. A formal tuple calculus semantics is outlined, and it is shown that this semantics reduces to the determinate semantics on determinate data.<>