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Generating Explanation Trees even for Negations in Deductive DataBase Systems

Although there were enormous research efforts on explanation and debugging tools for Prolog in the last years, good tools for bottom-up evaluating logic programming systems are still missing, since the generation of the underlying proof trees matches several problems in presence of negation and recursion. This paper wants to fill the gap and presents a source-to-source transformation to compute complete proof trees for bottom-up evaluating systems, so that advanced techniques, developed for top-down systems, will once be usable for bottom-up systems as well. The presented technique is implemented and in use in the deductive database system LOLA.