Games and total Datalog queries

We show that the expressive power of Datalog? programs under the well-founded semantics does not decrease when restricted to total programs thereby affirmatively answering an open question posed by Abiteboul et al. (Foundations of Databases, Addison-Wesley, Reading, MA, 1995, In particular, we show that for every such program there exists an equivalent total program whose only recursive rule is of the form win((X)overbar) <-- move((X)overbar), (Y)overbar), -win((Y)overbar), where move is definable by a quantifier-free first-order formula. Also, for the noninflationary semantics we derive a new normal form whose only recursive rule simulates a version of the game of life. (C) 2000 Elsevier Science B.V. All rights reserved.