© 1994 by Oxford University Press
Original Articles |
Explanation Closure, Action Closure and the Sandewall Test Suite for Reasoning about Change
Department of Computer Science, University of Rochester Rochester, NY 14627, USA. E-mail: schubert{at}cs.rochester.edu
Explanation closure (EC) axioms were previously introduced as a means of solving the frame problem. This paper provides a thorough demonstration of the power of EC combined with action closure (AC) for reasoning about dynamic worlds, by way of Sandewall's test suite of 12-or-so problems. Sandewall's problems range from the ‘Yale turkey shoot’ (and variants) to the ‘stuffy room’ problem, and are intended as a test and challenge for non-monotonic logics of action. The EC/AC-based solutions for the most part do not resort to non-monotonic reasoning at all, yet yield the intuitively warranted inferences in a direct, transparent fashion. While there are good reasons for ultimately employing non-monotonic or probabilistic logics—e.g. pervasive uncertainty and the qualification problem—this does show that the scope of monotonic methods has been underestimated. Subsidiary purposes of the paper are to clarify the intuitive status of EC axioms in relation to action effect axioms; and to show how EC, previously formulated within the situation calculus, can be applied within the framework of a temporal logic similar to Sandewall's ‘discrete fluent logic’, with some gains in clarity.
Keywords: Explanation closure,; action closure,; Sandewall test suite,; frame problem,; monotonic reasoning about change,; temporal logic.