Revisiting Acyclicity and Guardedness Criteria for Decidability of Existential Rules

Markus KrötzschMarkus Krötzsch, Sebastian RudolphSebastian Rudolph

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Markus Krötzsch, Sebastian Rudolph
Revisiting Acyclicity and Guardedness Criteria for Decidability of Existential Rules
Technical Report, Institut AIFB, KIT, volume 3011, January 2011

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KurzfassungAbstract
Existential rules, i.e. Datalog extended with existential quantifiers in rule heads, are currently studied under a variety of names such as Datalog+/-, forall-exists-rules, and tuple-generating dependencies. The renewed interest in this formalism is fuelled by a wealth of recently discovered language fragments for which query answering is decidable. This paper extends and consolidates two of the main approaches in this field -- acyclicity and guardedness -- by providing (1) complexity-preserving generalisations of weakly acyclic and weakly (frontier-)guarded rules, and (2) a novel formalism of glut-(frontier-)guarded rules that subsumes both. This builds on an insight that acyclicity can be used to extend any existential rule language while retaining decidability. Besides decidability, combined query complexities are established in all cases.
Bemerkung: Note: This technical report provides additional details for the paper Extending Decidable Existential Rules by Joining Acyclicity and Guardedness, which should usually be cited instead.
Forschungsgruppe:Research Group: Computational LogicComputational Logic, Wissensbasierte SystemeKnowledge-Based Systems

@techreport{KR2011,
  author      = {Markus Kr{\"{o}}tzsch and Sebastian Rudolph},
  title       = {Revisiting Acyclicity and Guardedness Criteria for Decidability
                 of Existential Rules},
  institution = {Institut {AIFB,} {KIT}},
  year        = {2011},
  month       = {January}
}