Hybrid Reasoning in BACK

Hybrid knowledge representation formalisms consist of two or more diierent subformalisms for representing diierent kinds of knowledge or knowledge in diierent kinds of representation formats. For a semantically well-founded hybrid formalism not only a precise semantics for each of the participating subformalisms has to be given but a semantics for the interrelationship between these subformalisms as well. A hybrid representation system therefore has to be implemented as a hybrid reasoning system taken into account these semantic models. The BACK system as an instance of this class of systems will be described with respect to the underlying semantic model and the demands for a reasoning component as one part of the realization of the formalism. The consequences and limits for the implementation of the BACK system are discussed.