Extending Decidable Existential Rules by Joining Acyclicity and Guardedness

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Markus Krötzsch, Sebastian Rudolph

Extending Decidable Existential Rules by Joining Acyclicity and Guardedness



Abstract. Existential rules, i.e. Datalog extended with existential quantifiers in rule heads, are currently studied under a variety of names such as Datalog+/–, ∀∃-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.

Published at IJCAI2011 (Conference paper)

Download PDF (last update: Apr 14 2011)

Citation details

  • Markus Krötzsch, Sebastian Rudolph. Extending Decidable Existential Rules by Joining Acyclicity and Guardedness. In Proceedings of the 22nd International Joint Conference on Artificial Intelligence (IJCAI-11), pp. 963–968. IJCAI 2011.

Remarks

This paper is based on the AIFB technical report Revisiting Acyclicity and Guardedness Criteria for Decidability of Existential Rules where full proofs can be found.

Topics

Rule languages

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