Note: Recognizing Helly Edge-Path-Tree graphs and their clique graphs

  • Authors:
  • Nicola Apollonio;Massimiliano Caramia

  • Affiliations:
  • Istituto per le Applicazioni del Calcolo, M. Picone, Via G. Amendola, 122/D, I-70126 Bari, Italy;Dipartimento di Ingegneria dell'Impresa, Universití di Roma "Tor Vergata", Via del Politecnico 1, I-00133 Roma, Italy

  • Venue:
  • Discrete Applied Mathematics
  • Year:
  • 2011

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Abstract

We present a unifying procedure for recognizing intersection graphs of Helly families of paths in a tree and their clique graphs. The Helly property makes it possible to look at these recognition problems as variants of the Graph Realization Problem, namely, the problem of recognizing Edge-Path-Tree matrices. Our result heavily relies on the notion of pie introduced in [M.C. Golumbic, R.E. Jamison, The edge intersection graphs of paths in a tree, Journal of Combinatorial Theory, Series B 38 (1985) 8-22] and on the observation that Helly Edge-Path-Tree matrices form a self-dual class of Helly matrices. Coupled to the notion of reduction presented in the paper, these facts are also exploited to reprove and slightly refine some known results for Edge-Path-Tree graphs.