Finite metrics in switching classes

  • Authors:
  • Andrzej Ehrenfeucht;Tero Harju;Grzegorz Rozenberg

  • Affiliations:
  • Department of Computer Science, University of Colorado at Boulder, Boulder, CO;Department of Mathematics, University of Turku, Turku, Finland;Department of Computer Science, University of Colorado at Boulder, Boulder, CO and Leiden Institute for Advanced Computer Science, Leiden University, Leiden, The Netherlands

  • Venue:
  • Discrete Applied Mathematics
  • Year:
  • 2007

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Abstract

Let g: D × D → R be a symmetric function on a finite set D satisfying g(x, x) = 0 for all x ∈ D. A switch gσ of g w.r.t. a local valuation σ: D → R is defined by gσ(x, y) = σ(x) + g(x, y) + σ(y) for x ≠ y and gσ(x, x) = 0 for all x. We show that every symmetric function g has a unique minimal semimetric switch, and, moreover, there is a switch of g that is isometric to a finite Manhattan metric. Also, for each metric on D, we associate an extension metric on the set of all nonempty subsets of D, and we show that this extended metric inherits the switching classes on D.