On the Exploration of the Query Rewriting Space with Existential Rules

König, Mélanie; Leclère, Michel; Mugnier, Marie-Laure; Thomazo, Michaël

doi:10.1007/978-3-642-39666-3_10

Cited by 13 publications

(13 citation statements)

References 11 publications

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“…An FO-rewriting of q and Σ in the form of a UCQ is called a UCQ-rewriting of q and Σ. (That the BDDP of Σ is equivalent to the existence of UCQ-rewritings for all CQs over Σ can be shown using an earlier result from graph databases [57] and the fact that minimal UCQ-rewritings are unique up to isomorphism [36]; an ontology with UCQ-rewritings for all CQs is called a finite unification set by Baget et al [6]. )…”

Section: First-order Rewritability: Size Of Rewritings Mattersmentioning

confidence: 99%

The price of query rewriting in ontology-based data access

Gottlob

Kikot

Kontchakov

et al. 2014

Artificial Intelligence

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We give a solution to the succinctness problem for the size of first-order rewritings of conjunctive queries in ontologybased data access with ontology languages such as OWL 2 QL, linear Datalog ± and sticky Datalog ± . We show that positive existential and nonrecursive datalog rewritings, which do not use extra non-logical symbols (except for intensional predicates in the case of datalog rewritings), suffer an exponential blowup in the worst case, while first-order rewritings can grow superpolynomially unless NP ⊆ P/poly. We also prove that nonrecursive datalog rewritings are in general exponentially more succinct than positive existential rewritings, while first-order rewritings can be superpolynomially more succinct than positive existential rewritings. On the other hand, we construct polynomial-size positive existential and nonrecursive datalog rewritings under the assumption that any data instance contains two fixed constants.

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Section: First-order Rewritability: Size Of Rewritings Mattersmentioning

confidence: 99%

The price of query rewriting in ontology-based data access

Gottlob

Kikot

Kontchakov

et al. 2014

Artificial Intelligence

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“…We keep below the definitions introduced in [KLMT13], while pointing out that, in the context of this paper, the rules R 1 . .…”

Section: Aggregated-piece Based Operatormentioning

confidence: 99%

Sound, complete and minimal UCQ-rewriting for existential rules

König

Leclère

Mugnier

et al. 2015

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We address the issue of Ontology-Based Data Access, with ontologies represented in the framework of existential rules, also known as Datalog±. A wellknown approach involves rewriting the query using ontological knowledge. We focus here on the basic rewriting technique which consists of rewriting the initial query into a union of conjunctive queries. First, we study a generic breadth-first rewriting algorithm, which takes any rewriting operator as a parameter, and define properties of rewriting operators that ensure the correctness of the algorithm. Then, we focus on piece-unifiers, which provide a rewriting operator with the desired properties. Finally, we propose an implementation of this framework and report some experiments.

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“…-Search space. Another typical metric for query rewriting algorithms is the number of CQs explored and generated during the rewriting [König et al 2013]. In case of XRewrite, the explored queries are those labelled with e, while the generated ones are those obtained via a rewriting step (possibly multiple times).…”

Section: Experimental Settingmentioning

confidence: 99%

Query Rewriting and Optimization for Ontological Databases

Gottlob

Orsi

Pieris

2014

ACM Trans. Database Syst.

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Ontological queries are evaluated against a knowledge base consisting of an extensional database and an ontology (i.e., a set of logical assertions and constraints which derive new intensional knowledge from the extensional database), rather than directly on the extensional database. The evaluation and optimization of such queries is an intriguing new problem for database research. In this paper, we discuss two important aspects of this problem: query rewriting and query optimization. Query rewriting consists of the compilation of an ontological query into an equivalent first-order query against the underlying extensional database. We present a novel query rewriting algorithm for rather general types of ontological constraints which is well-suited for practical implementations. In particular, we show how a conjunctive query against a knowledge base, expressed using linear and sticky existential rules, that is, members of the recently introduced Datalog ± family of ontology languages, can be compiled into a union of conjunctive queries (UCQ) against the underlying database. Ontological query optimization, in this context, attempts to improve this rewriting process so to produce possibly small and cost-effective UCQ rewritings for an input query.

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On the Exploration of the Query Rewriting Space with Existential Rules

Cited by 13 publications

References 11 publications

The price of query rewriting in ontology-based data access

The price of query rewriting in ontology-based data access

Sound, complete and minimal UCQ-rewriting for existential rules

Query Rewriting and Optimization for Ontological Databases

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