Default reasoning with preference within only knowing logic

The main construction in this paper is an encoding of default logic into an "only knowing" logic with degrees of confidence. By imposing simple and natural constraints on the encoding we show that the "only knowing" logic can accommodate ordered default theories and that the constrained encoding implements a prescriptive interpretation of preference between defaults. An advantage of the encoding is that it provides a transparent formal rendition of such a semantics. A feature of the construction is that the generation of extensions can be carried out within the "only knowing" logic, using object level concepts alone.