Updates in answer set programming: An approach based on basic structural properties

We have studied the update operator 1 de ned for update sequences by Eiter et al. without tautologies and we have observed that it satis es an interesting property. This property, which we call Weak Independence of Syntax (WIS), is similar to one of the postulates proposed by Alchourr on, G ardenfors, and Makinson (AGM); only that in this case it applies to nonmonotonic logic. In addition, we consider other ve additional basic properties about update programs and we show that 1 satis es them. This work continues the analysis of the AGM postulates with respect to the 1 operator under a re ned view that considers N2 as a monotonic logic which allows us to expand our understanding of answer sets. Moreover, N2 helped us to derive an alternative de nition of 1 avoiding the use of unnecessary extra atoms.