The need for control in logic programs is now being recognized. This is particularly evident when one focuses on allowing updates in logic programs. In this paper we propose a language DatalogA which is an extension of Datalog with updates to base relations. We define some procedural constructs to allow update programs to be written in an easy manner. The (W,p) scheme of Dynamic Logic fits nicely into the semantics of DatalogA programs in which W is taken to be the set of all possible states of the program and p is the accessibility relation between states. We give declarative semantics and equivalent constructed model semantics for DatalogA programs. We show that in the absence of updates our semantics reduce to the classical semantics of Datalog. Finally, we show some examples of non-stratified programs expressed in DatalogA.
