Distances between languages and reflexivity of relations

  • Authors:
  • Christian Choffrut;Giovanni Pighizzini

  • Affiliations:
  • LIAFA, Université Paris 7, 2, Pl. Jussieu 75 251 Paris Cedex 05, France;Dipartimento di Scienze dell'Informazione, Università degli Studi di Milano, via Comelico, 39, I-20135 Milano, Italy

  • Venue:
  • Theoretical Computer Science
  • Year:
  • 2002

Quantified Score

Hi-index 5.23

Visualization

Abstract

We extend the Hamming, edit, prefix, suffix and subword distances between strings to subsets of strings. We show that computing these distances between two rational subsets reduces to computing the weight of an automaton "with distance function" as introduced by Hashiguchi (this latter notion of distance has nothing to do with our notion). We make a step further by extending the notion of distance between subsets to that of "almost reflexivity" of relations over strings: intuitively a relation is almost reflexive if every element of its domain is in relation with some "close" element in its range and vice versa. Various properties connected to almost reflexivity are investigated. With two exceptions, their decidability status relative to the five notions of distances is settled for the three families of recognizable, synchronous and deterministic relations.