Controlled Use of Clausal Lemmas in Connection TableauCalculiMarc

b b b b b b b b b b b b b b b b b b b Abstract Proof procedures based on model elimination or the connection tableau calculus have become more and more successful in the past. But these procedures still suuer from long proof lengths as well as from a rather high degree of redundant search eeort in comparison to resolution-style search procedures. In order to overcome these problems we investigate the use of clausal lemmas. We develop a method to augment a given set of clauses with a lemma set in a preprocessing phase and discuss the ability of this technique to reduce proof lengths and to provide an appropriate reordering of the search space. We deal with the basic connection tableau calculus as well as with several calculus reenements and extensions. In order to control the use of lemmas we develop techniques for selecting relevant lemmas based on similarity criteria. Experiments with the prover Setheo performed in several domains demonstrate the high potential of our approach.