Indefinite Constraint Databases with Temporal Information: Representational Power and Computational Complexity

We develop the scheme of indefinite constraint databases using first-order logic as our representation language. When this scheme is instantiated with temporal constraints, the resulting formalism is more expressive than standard temporal constraint networks. The extra representational power allows us to express temporal knowledge and queries that have been impossible to express before. To make our claim more persuasive, we survey previous works on querying temporal constraint networks and show that they can be viewed as an instance of the scheme of indefinite constraint databases. Then we study the computational complexity of the proposed scheme when constraints are temporal, and carefully outline the boundary between tractable and intractable query answering problems.