  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.
