Temporal Indeterminacy in Deductive Databases: An Approach Based on Event Calculus

Abstract

In this paper, we deal with the notion of temporal indeterminacy in temporal deductive databases. We adopt Kowalski and Sergot's Event Calculus (1986, 1992) as our data model. To the best of our knowledge, no previous research efforts have been devoted to introduce indeterminacy in the Event Calculus (EC). We first motivate the need for indeterminacy in real world applications. Then, after briefly presenting EC, we illustrate in detail our proposal (TIC, Temporal Indeterminacy event Calculus). From a description of events whose precise temporal occurrence is unknown, and a description of the properties initiated or terminated by those events, TIC derives intervals over which properties are necessarily valid, and intervals of indeterminacy for the initiating and terminating instants of the properties. Although we adopt EC as our ontology, the proposed ideas can be reformulated for adoption in other approaches. TIC is presented both informally and formally, and illustrated with several examples. Finally, we discuss completeness and complexity issues of TIC.