Default logic generalized and simplified
We study a generalization of default logic obtained by extending its logical, monotonic basis to disjunctive (multiple-conclusion) rules. Special attention will be paid to the representation opportunities created by such rules, in particular to the use of default justifications in the heads of the rules. On the other hand, it will be shown that even the generalized default logic can be simplified to a formal system that involves only monotonic inference rules and unconditional ('supernormal') default assumptions.
default logic default assumptions disjunctive rules