Consistency checking reduced to satisfiability of concepts in terminological systems

We investigate the inference problem in knowledge representation systems of theKl-one family. These systems, also called terminological systems, are equipped with concept languages that are used to express the conceptual knowledge of a problem domain in a structured way. In order to reason with the represented knowledge, terminological systems provide a couple of inference services. In this paper we show that the main reasoning problems in expressive concept languages can be reduced to a particular inference problem, namely checking satisfiability of concepts. This result has two important applications. From a practical point of view, our reduction together with the existence of relatively efficient implementations of satisfiability algorithms strongly simplifies the implementation of inference algorithms in terminological systems. Even from a complexity point of view, the result shows that in the underlying concept language interesting inference problems such as consistency checking or query answering are not harder (in terms of the worst case complexity) than satisfiability checking of concepts.