A critical problem for practical KR is dealing with relationships that change over time. This problem is compounded by representation languages such as OWL that are biased towards binary relations; even when the relationships that vary with time are binary, the time the relationship holds typically requires a third argument. We discuss the standard approach to this problem, and contrast it to a new alternative based on a four-dimensionalist (perdurantist) ontology, which allows us to use more of the expressive power of description logics. The technique is usable in other logics as well. Keywords. Ontologies, Semantic Web, Time, Fluents.
Christopher A. Welty, Richard Fikes