Journal of Logic and Computation Advance Access originally published online on November 21, 2008
Journal of Logic and Computation 2009 19(2):263-302; doi:10.1093/logcom/exn073
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Corner Article |
Paramodulation with Well-founded Orderings
Universitat de Girona, Department IMA, Girona, Spain.
E-mail: mbofill{at}ima.udg.edu
Universitat Politècnica de Catalunya, Department LSI, Barcelona, Spain.
E-mail: rubio{at}lsi.upc.edu
Received 18 January 2008.
| Abstract |
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For many years, all existing completeness results for Knuth–Bendix completion and ordered paramodulation required the term ordering
to be well-founded, monotonic and total(izable) on ground terms. Then, it was shown that well-foundedness and the subterm property were enough for ensuring completeness of ordered paramodulation. Here we show that the subterm property is not necessary either. By using a new restricted form of rewriting, we obtain a completeness proof of ordered paramodulation for Horn clauses with equality, where well-foundedness of the ordering suffices. Apart from the theoretical significance of this result, some potential applications motivating the interest of dropping the subterm property are given. The proof of the results included in this article, being still technical in some parts, is pretty much shorter and easier to read than the one we have in the preliminary version of this work presented at the CADE, 2002 conference (Bofill, and Rubio, 2002, CADE, Vol. 2392 of LNAI, pp. 456–470).
Keywords: Term rewriting; equational reasoning; theorem proving; paramodulation; Knuth–Bendix completion