Reasoning about Concurrent Actions and Observations

In this paper we present an experiment by using abductive logic programming to reason about concurrent actions and observations. Technically, we extend Gelfond and Lifschitz' action description language A with concurrent actions and observation propositions to describe the ideal behaviour of domains of (concurrent) actions and practically observed behaviour, respectively, without requiring that the practically observed behaviour of a domain of actions be consistent with its ideal behaviour. We present a translation from domain descriptions and observations in the new action language to abductive normal logic programs. The translation is shown to be both sound and complete. From the standpoint of diagnosis, in particular, we discuss the temporal explanation of inferring actions from fluent changes at two different levels, namely, at the domain description level and at the abductive logic programming level. The method is applicable to the temporal projection problem with incomplete infor..