Uncertainty management in logic programming: simple and effective top-down query answering

We present a simple, yet general top-down query answering procedure for logic programs managing uncertainty. The main features are: ii{i} the certainty values are taken from a certainty lattice; ii{ii} computable functions may appear in the rule bodies to manipulate certainties; and ii{iii} we solve the problem by a reduction to an equational systems, for which we device a top-down procedure.