Historical Indeterminacy

In historical 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. We present the possible tuples data model, in which each indeterminate event is represented with a set of possible events that delimits when the event might have occurred, and a probability distribution over that set. We extend the TQuel query language with constructs that specify the user's credibility in the underlying historical data and in the user's plausibility in the relationships among that data. We provide a formal tuple calculus semantics, and show that this semantics reduces to the determinate semantics. We outline an e cient representation of historical indeterminacy, and e cient query processing algorithms, demonstrating the practicality of our proposed approach. 1 Department of Computer Science University of Arizona Tucson, AZ 85721 fcurtis,[email protected]