In this paper we present a theory for reasoning about actions which is based on Dynamic Linear Time Temporal Logic . DLTL is a simple extension of propositional temporal logic of linear time in which regular programs of propositional dynamic logic can be used for indexing temporal modalities. The action theory we define allows to reason with incomplete initial states, to do postdiction and to deal with ramifications and with nondeterministic actions, which are captured by possibly alternative extensions . The (...) expressiveness of temporal logic is exploited to enhance the action language by allowing the definition of general temporal constraints as well as complex actions in the specification of the domain description. We show that the temporal projection problem and the planning problem can be modelled as satisfiability problems in DLTL. (shrink)

ABSTRACT This paper defines a new modal logic based theory for non-monotonic reasoning. This logic expresses notions about hypotheses and known information. These notions are defined in the framework of the modal system τ. A translation of default logic in terms of hypothesis theory is given with which it is possible to fully characterize default logic by giving a necessary and sufficient criterion for the existence and the non-existence of extensions. Moreover several problems relating to non-monotonic reasoning are discussed (and (...) solutions are presented), such as case analysis, multiple extensions and contraposition. (shrink)