We address the problem of representing preferences among sets of properties (outcomes, desiderata, etc.) in default logic. In this approach, an ordered default theory consists of default rules, world knowledge, and preferences on sets of default rules. An ordered theory is transformed into a second, standard default theory wherein the preferences are respected, in that defaults are applied in the specified order and a set of order-equivalent defaults is applied only en masse. This translation is accomplished via the naming of defaults, so that reference may be made to default rules and sets of default rules from within a theory. The approach differs from previous work in that we obtain standard default theories, and do not rely on prioritised versions as do other approaches. In practical terms this means we can immediately use existing default logic theorem provers for an implementation. From a theoretical point of view, this shows that the explicit representation of priorities among sets of defaults adds nothing to the overall expressibility of default logic.
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