Temporal Entities - Types, Tokens and Qualifications

Reified logics have been a major subject of interest in the knowledge representation community for well over twenty years, since over the years, the need to quantify and reason about propositional entities such as events and states among other temporal entities has grown. Galton had made it clear that one may either refer to types or tokens (instances) of such entities in the ontology. A clear tendency in the literature is to derive event tokens from event types by instantiating types with their times of occurrence. That tendency is exemplified by earlier token-reified logic. The problem with this approach is that it makes it difficult to distinguish between two different events of the same type happening at the same time. This is a major price that earlier logic paid for being a full-fledged logical theory. This paper presents an alternative way of deriving event tokens from event types which uses the concept of qualifications rather than use times of occurrence. A clear distinction is made between qualifications and the actual event tokens they help derive from event types. A qualification captures the peculiarities of an actual event token that are not part of the event type definitions. Our logic maintains both the advantage of being a full-fledged logic as well being able to add many qualifications to an event token.