Query Answering under Expressive Entity-Relationship Schemata

  • Andrea Calì
  • Georg Gottlob
  • Andreas Pieris
Part of the Lecture Notes in Computer Science book series (LNCS, volume 6412)


We address the problem of answering conjunctive queries under constraints representing schemata expressed in an extended version of the Entity- Relationship model. This extended model, called ER +  model, comprises is-a constraints among entities and relationships, plus functional and mandatory participation constraints. In particular, it allows arbitrary permutations of the roles in is-a among relationships. A key notion that ensures high tractability in ER +  schemata is separability, i.e., the absence of interaction between the functional participation constraints and the other constructs of ER + .We provide a precise syntactic characterization of separable ER +  schemata, called ER± schemata, by means of a necessary and sufficient condition. We present a complete complexity analysis of the conjunctive query answering problem under ER± schemata. We show that the addition of so-called negative constraints does not increase the complexity of query answering. With such constraints, our model properly generalizes the most widely-adopted tractable ontology languages.


Data Complexity Description Logic Relational Schema Conjunctive Query Query Answer 
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 2010

Authors and Affiliations

  • Andrea Calì
    • 3
    • 2
  • Georg Gottlob
    • 1
    • 2
  • Andreas Pieris
    • 1
  1. 1.Computing LaboratoryUniversity of OxfordUK
  2. 2.Oxford-Man Institute of Quantitative FinanceUniversity of OxfordUK
  3. 3.Department of Information Systems and ComputingBrunel UniversityUK

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