Transformations of Logic Programs Related to Causality and Planning

		Esra Erdem and Vladimir Lifschitz
        	  University of Texas at Austin

We prove two properties of logic programs under the answer set semantics
that may be useful in connection with applications of logic programming to
representing causality and to planning.  One theorem is about the use of
disjunctive rules to express that an atom is exogenous. The other provides
an alternative way of expressing that a plan does not include concurrently
executed actions.