License: Creative Commons Attribution 3.0 Unported license (CC BY 3.0)
When quoting this document, please refer to the following
DOI: 10.4230/LIPIcs.RTA.2015.209
URN: urn:nbn:de:0030-drops-51986
Go to the corresponding LIPIcs Volume Portal

Hirokawa, Nao ; Middeldorp, Aart ; Moser, Georg

Leftmost Outermost Revisited

18.pdf (0.5 MB)


We present an elementary proof of the classical result that the
leftmost outermost strategy is normalizing for left-normal orthogonal rewrite systems. Our proof is local and extends to hyper-normalization and weakly orthogonal systems. Based on the new proof, we study basic normalization, i.e., we study normalization if the set of considered starting terms is restricted to basic terms. This allows us to weaken the left-normality restriction. We show that the leftmost outermost strategy is hyper-normalizing for basically left-normal orthogonal rewrite systems. This shift of focus greatly extends the applicability of the classical result, as evidenced by the experimental data provided.

BibTeX - Entry

  author =	{Nao Hirokawa and Aart Middeldorp and Georg Moser},
  title =	{{Leftmost Outermost Revisited}},
  booktitle =	{26th International Conference on Rewriting Techniques and Applications (RTA 2015)},
  pages =	{209--222},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-85-9},
  ISSN =	{1868-8969},
  year =	{2015},
  volume =	{36},
  editor =	{Maribel Fern{\'a}ndez},
  publisher =	{Schloss Dagstuhl--Leibniz-Zentrum fuer Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{},
  URN =		{urn:nbn:de:0030-drops-51986},
  doi =		{10.4230/LIPIcs.RTA.2015.209},
  annote =	{Keywords: term rewriting, strategies, normalization}

Keywords: term rewriting, strategies, normalization
Collection: 26th International Conference on Rewriting Techniques and Applications (RTA 2015)
Issue Date: 2015
Date of publication: 18.06.2015

DROPS-Home | Fulltext Search | Imprint | Privacy Published by LZI