Monadic Datalog Containment

  • Michael Benedikt
  • Pierre Bourhis
  • Pierre Senellart
Part of the Lecture Notes in Computer Science book series (LNCS, volume 7392)


We reconsider the problem of containment of monadic datalog (MDL) queries in unions of conjunctive queries (UCQs). Prior work has dealt with special cases, but has left the precise complexity characterization open. We begin by establishing a 2EXPTIME lower bound on the MDL/UCQ containment problem, resolving an open problem from the early 90’s. We then present a general approach for getting tighter bounds on the complexity, based on analysis of the number of mappings of queries into tree-like instances. We use the machinery to present an important case of the MDL/UCQ containment problem that is in co-NEXPTIME, and a case that is in EXPTIME. We then show that the technique can be used to get a new tight upper bound for containment of tree automata in UCQs. We show that the new MDL/UCQ upper bounds are tight.


Access Method Conjunctive Query Tree Automaton Tree Pattern Query Datalog Program 
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 2012

Authors and Affiliations

  • Michael Benedikt
    • 1
  • Pierre Bourhis
    • 1
  • Pierre Senellart
    • 2
  1. 1.Oxford UniversityOxfordUnited Kingdom
  2. 2.Institut Mines–Télécom; Télécom ParisTech; CNRS LTCIParisFrance

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