Combining Existential Rules and Transitivity: Next Steps

04/28/2015
by   Jean Francois Baget, et al.
0

We consider existential rules (aka Datalog+) as a formalism for specifying ontologies. In recent years, many classes of existential rules have been exhibited for which conjunctive query (CQ) entailment is decidable. However, most of these classes cannot express transitivity of binary relations, a frequently used modelling construct. In this paper, we address the issue of whether transitivity can be safely combined with decidable classes of existential rules. First, we prove that transitivity is incompatible with one of the simplest decidable classes, namely aGRD (acyclic graph of rule dependencies), which clarifies the landscape of `finite expansion sets' of rules. Second, we show that transitivity can be safely added to linear rules (a subclass of guarded rules, which generalizes the description logic DL-Lite-R) in the case of atomic CQs, and also for general CQs if we place a minor syntactic restriction on the rule set. This is shown by means of a novel query rewriting algorithm that is specially tailored to handle transitivity rules. Third, for the identified decidable cases, we pinpoint the combined and data complexities of query entailment.

READ FULL TEXT

page 1

page 2

page 3

page 4

research
12/15/2014

Worst-case Optimal Query Answering for Greedy Sets of Existential Rules and Their Subclasses

The need for an ontological layer on top of data, associated with advanc...
research
12/12/2015

Query Answering over Contextualized RDF/OWL Knowledge with Forall-Existential Bridge Rules: Decidable Finite Extension Classes (Post Print)

The proliferation of contextualized knowledge in the Semantic Web (SW) h...
research
09/06/2022

Finite-Cliquewidth Sets of Existential Rules: Toward a General Criterion for Decidable yet Highly Expressive Querying

In our pursuit of generic criteria for decidable ontology-based querying...
research
07/01/2020

Decidable Entailments in Separation Logic with Inductive Definitions: Beyond Established Systems

We define a class of Separation Logic formulae, whose entailment problem...
research
07/17/2023

Derivation-Graph-Based Characterizations of Decidable Existential Rule Sets

This paper establishes alternative characterizations of very expressive ...
research
06/09/2023

Query Rewriting with Disjunctive Existential Rules and Mappings

We consider the issue of answering unions of conjunctive queries (UCQs) ...

Please sign up or login with your details

Forgot password? Click here to reset