Upward Straight-Line Embeddings of Directed Graphs into Point Sets

  • Authors:
  • Alejandro Estrella-Balderrama;Fabrizio Frati;Stephen G. Kobourov

  • Affiliations:
  • Department of Computer Science, University of Arizona, U.S.A.;Dipartimento di Informatica e Automazione, Università di Roma Tre,;Department of Computer Science, University of Arizona, U.S.A.

  • Venue:
  • Graph-Theoretic Concepts in Computer Science
  • Year:
  • 2008

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Abstract

In this paper we consider the problem of characterizing the directed graphs that admit an upward straight-line embedding into every point set in convex or in general position. In particular, we show that no biconnected directed graph admits an upward straight-line embedding into every point set in convex position, and we provide a characterization of the Hamiltonian directed graphs that admit upward straight-line embeddings into every point set in general or in convex position. We also describe how to construct upward straight-line embeddings of directed paths into convex point sets and we prove that for directed trees such embeddings do not always exist. Further, we investigate the related problem of upward simultaneous embedding without mapping, proving that deciding whether two directed graphs admit an upward simultaneous embedding without mapping is $\cal NP$-hard.