Published online by Cambridge University Press: 01 November 2008
We introduce an extended tableau calculus for answer set programming (ASP). Theproof system is based on the ASP tableaux defined in the work by Gebser andSchaub (Tableau calculi for answer set programming. In Proceedings ofthe 22nd International Conference on Logic Programming (ICLP 2006),S. Etalle and M. Truszczynski, Eds. Lecture Notes in Computer Science, vol.4079. Springer, 11–25) with an added extension rule. We investigatethe power of Extended ASP Tableaux both theoretically and empirically. We studythe relationship of Extended ASP Tableaux with the Extended Resolution proofsystem defined by Tseitin for sets of clauses, and separate Extended ASPTableaux from ASP Tableaux by giving a polynomial-length proof for a family ofnormal logic programs {Φn} for which ASP Tableaux has exponential-length minimal proofs withrespect to n. Additionally, Extended ASP Tableaux implyinteresting insight into the effect of program simplification on the lengths ofproofs in ASP. Closely related to Extended ASP Tableaux, we empiricallyinvestigate the effect of redundant rules on the efficiency of ASP solving.