Iterated Logic Program Updates

The eld of theory update has seen some improvement, in what regards updating, by allowing desired updates to be speci ed by update programs. The updating of models is governed by update rules, as well as by inertia applied to those literals not directly a ected by the update program. Though this is important, it remains necessary to tackle too the updating of theories speci ed by programs. In this paper we explore logic program updates, namely how to exert inertia on program rules rather than on the literals of their models. We de ne program updates and characterize them semantically, both for the 2-valued and the 3-valued cases. We also de ne iterated logic program updating, a crucial notion inasmuch as it allows us to conceive what it is to successively update one program by another, and so to prescribe the evolution of knowledge bases by means of updates.