Join-Reachability Problems in Directed Graphs

  • Loukas Georgiadis
  • Stavros D. Nikolopoulos
  • Leonidas Palios
Part of the Lecture Notes in Computer Science book series (LNCS, volume 6651)

Abstract

For a given collection \(\mathcal{G}\) of directed graphs we define the join-reachability graph of \(\mathcal{G}\), denoted by \(\mathcal{J}(\mathcal{G})\), as the directed graph that, for any pair of vertices a and b, contains a path from a to b if and only if such a path exists in all graphs of \(\mathcal{G}\). Our goal is to compute an efficient representation of \(\mathcal{J}(\mathcal{G})\). In particular, we consider two versions of this problem. In the explicit version we wish to construct the smallest join-reachability graph for \(\mathcal{G}\). In the implicit version we wish to build an efficient data structure (in terms of space and query time) such that we can report fast the set of vertices that reach a query vertex in all graphs of \(\mathcal{G}\). This problem is related to the well-studied reachability problem and is motivated by emerging applications of graph-structured databases and graph algorithms. We consider the construction of join-reachability structures for two graphs and develop techniques that can be applied to both the explicit and the implicit problem. First we present optimal and near-optimal structures for paths and trees. Then, based on these results, we provide efficient structures for planar graphs and general directed graphs.

Keywords

Span Tree Directed Graph Unoriented Tree Query Time Reachability Problem 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2011

Authors and Affiliations

  • Loukas Georgiadis
    • 1
  • Stavros D. Nikolopoulos
    • 2
  • Leonidas Palios
    • 2
  1. 1.Department of Informatics and Telecommunications EngineeringUniversity of Western MacedoniaGreece
  2. 2.Department of Computer ScienceUniversity of IoanninaGreece

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