In this paper we propose a logic programming language which supports hypothetical updates together with integrity constraints. The language allows sequences of updates by sets of atoms and it makes use of a revision mechanism to restore consistency when an update violates some integrity constraint. The revision policy we adopt is based on the simple idea that more recent information is preferred to earlier one. This language can be used to perform several types of defeasihle reasoning. We define a goal-directed proof procedure for the language and develope a logical characterization in a modal logic by introducing an abductive semantics.
Dov M. Gabbay, Laura Giordano, Alberto Martelli, N