Proof Lengths for Equational Completion David A. Plaisted University of North Carolina at Chapel Hill Chapel Hill, NC 27599-3175, USA E-mail: plaisted@cs.unc.edu Andrea Sattler-Klein Fachbereich Informatik, Universitaet Kaiserslautern D-67663 Kaiserslautern, GERMANY E-mail: sattler@informatik.uni-kl.de Abstract We first show that ground term-rewriting systems can be completed in a polynomial number of rewriting steps, if the appropriate data structure for terms is used. We then apply this result to study the lengths of critical pair proofs in non-ground systems, and obtain bounds on the lengths of critical pair proofs in the non-ground case. We show how these bounds depend on the types of inference steps that are allowed in the proofs. Keywords completion, term rewriting, proof length, ground systems Source anonymous FTP server ftp.uni-kl.de [131.246.94.94] path: /reports_uni-kl/computer_science/SEKI/1995/ file: Sattler.SR-95-06.ps.gz