A modal logic for subjective default reasoning

摘要

In this paper we introduce DML: Default Modal Logic. DML is a logic endowed with a two-place modal connective that has the intended meaning of “If α, then normally β”. On top of providing a well-defined tool for analyzing common default reasoning, DML allows nesting of the default operator. We present a semantic framework in which many of the known default proof systems can be naturally characterized, and prove soundness and completeness theorems for several such proof systems.