Updates in Answer Set Programming: An Approach Based on Basic Structural   Properties
  We have studied the update operator defined for update sequences by Eiter et al. without tautologies and we have observed that it satisfies an interesting property This property, which we call Weak Independence of Syntax (WIS), is similar to one of the postulates proposed by Alchourron, Gardenfors, and Makinson (AGM); only that in this case it applies to nonmonotonic logic. In addition, we consider other five additional basic properties about update programs and we show that the operator of Eiter et al. satisfies them. This work continues the analysis of the AGM postulates under a refined view that considers nelson logic as a monotonic logic which allows us to expand our understanding of answer sets. Moreover, nelson logic helped us to derive an alternative definition of the operator defined by Eiter et al. avoiding the use of unnecessary extra atoms. 
Mauricio Osorio and V\'ictor Cuevas