Universität Bielefeld - Sonderforschungsbereich 360

Computational Properties of Spatial and Temporal Calculi

Bernhard Nebel
Natural language understanding and generation, planning, diagnosis and knowledge representation have to deal with qualitative spatial and temporal representation and reasoning. For this purpose, a number of specialized calculi have been developed, which are all based on constraint satisfaction.

Not very surprisingly, all the calculi turned out to be NP-hard, but there are interesting fragments that lead to polynomial-time algorithms. However, there is not much work on determining the practical boundaries for solving spatial and temporal reasoning problems in practice.

In the talk, I will introduce the two most common temporal and spatial calculi and report on their worst-case computational properties and on the tractability of fragments. Further, I present the results of a set of experiments performed on temporal reasoning instances. These give an indication where the "really hard" instances are and support the conclusion that the ORD-HORN relations can indeed be used to realize efficient inference methods.


Anke Weinberger, 1995-11-20