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Towards a Characterization of Order-Invariant Queries over Tame Structures

  • Michael Benedikt
  • Luc Segoufin
Part of the Lecture Notes in Computer Science book series (LNCS, volume 3634)

Abstract

This work deals with the expressive power of logics on finite structures with access to an additional “arbitrary” linear order. The queries that can be expressed this way are the order-invariant queries for the logic. For the standard logics used in computer science, such as first-order logic, it is known that access to an arbitrary linear order increases the expressiveness of the logic. However, when we look at the separating examples, we find that they have satisfying models whose Gaifman Graph is complex – unbounded in valence and in treewidth. We thus explore the expressiveness of order-invariant queries over graph-theoretically well-behaved structures. We prove that first-order order-invariant queries over strings and trees have no additional expressiveness over first-order logic in the original signature. We also prove new upper bounds on order-invariant queries over bounded treewidth and bounded valence graphs. Our results make use of a new technique of independent interest: the application of algebraic characterizations of definability to show collapse results.

Keywords

Linear Order Turing Machine Order Logic Colored Graph Regular Language 
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 2005

Authors and Affiliations

  • Michael Benedikt
    • 1
  • Luc Segoufin
    • 2
  1. 1.Bell LaboratoriesLisleUSA
  2. 2.INRIA-FutursParc-Club Orsay universityOrsay CedexFrance

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