Contextual abduction and its complexity issues

Abstract

In everyday life, it seems that we prefer some explanations for an observation over others because of our contextual background knowledge. Reiter already tried to specify a mechanism within logic that allows us to avoid explicitly considering all exceptions in order to derive a conclusion w.r.t. the usual case. In a recent paper, a contextual reasoning approach has been presented, which takes this contextual background into account and allows us to specify contexts within the logic. This approach is embedded into the Weak Completion Semantics, a Logic Programming approach that aims at adequately modeling human reasoning tasks. As this approach extends the underlying three-valued Lukasiewicz logic, some formal properties of the Weak Completion Semantics do not hold anymore. In this paper, we investigate the effects of this extension and present some surprising results about the complexity issues of contextual abduction