Laws of Generalized Prioritization Extended Abstract

Giving a semantics to an inheritance hierarchy, or more generally to a set of prioritized defaults, can be done using the lexicographic ordering, rst used by 5] for circumscription. The technique can be extended to any preferential logic, as noted in 2], where it is dubbed generalized prioritization. It has also been used independently in 9, 12]. In this paper we examine how important properties of preference relations propagate through lexicographic deenition, and the algebraic laws satissed by this technique. To express them we build a theory of operators on preferences.