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Idempotent Anti-unification

Published: 02 November 2019 Publication History

Abstract

In this article, we address two problems related to idempotent anti-unification. First, we show that there exists an anti-unification problem with a single idempotent symbol that has an infinite minimal complete set of generalizations. It means that anti-unification with a single idempotent symbol has infinitary or nullary generalization type, similar to anti-unification with two idempotent symbols, shown earlier by Loïc Pottier. Next, we develop an algorithm that takes an arbitrary idempotent anti-unification problem and computes a representation of its solution set in the form of a regular tree grammar. The algorithm does not depend on the number of idempotent function symbols in the input terms. The language generated by the grammar is the minimal complete set of generalizations of the given anti-unification problem, which implies that idempotent anti-unification is infinitary.

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cover image ACM Transactions on Computational Logic
ACM Transactions on Computational Logic  Volume 21, Issue 2
April 2020
316 pages
ISSN:1529-3785
EISSN:1557-945X
DOI:10.1145/3371152
  • Editor:
  • Orna Kupferman
Issue’s Table of Contents
Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for components of this work owned by others than the author(s) must be honored. Abstracting with credit is permitted. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from [email protected].

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Publication History

Published: 02 November 2019
Accepted: 01 August 2019
Revised: 01 June 2019
Received: 01 January 2019
Published in TOCL Volume 21, Issue 2

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Author Tags

  1. Anti-unification
  2. generalization
  3. idempotence
  4. regular tree grammar

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