SPARQL Query Containment under RDFS Entailment Regime

Chekol, Melisachew Wudage; Euzenat, Jérôme; Genevès, Pierre; Layaïda, Nabil

doi:10.1007/978-3-642-31365-3_13

Cited by 29 publications

(23 citation statements)

References 13 publications

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“…In [5], a 2-EXPTIME upper bound was proved for containment under RDFS entailment of SPARQL queries that contain only the AND and UNION operator as well as property paths. For a similar query fragment, but instead of RDFS taking ontologies in the Description Logic SHI into account, the same upper bound was proved in [6].…”

Section: Related Workmentioning

confidence: 99%

Containment and equivalence of well-designed SPARQL

Pichler

Skritek

2014

Proceedings of the 33rd ACM SIGMOD-SIGACT-SIGART Symposium on Principles of Database Systems

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Query containment and query equivalence constitute important computational problems in the context of static query analysis and optimization. While these problems have been intensively studied for fragments of relational calculus, almost no works exist for the semantic web query language SPARQL. In this paper, we carry out a comprehensive complexity analysis of containment and equivalence for several fragments of SPARQL: we start with the fundamental fragment of well-designed SPARQL restricted to the AND and OPTIONAL operator. We then study basic extensions in the form of the UNION operator and/or projection. The results obtained range from NP-completeness to undecidability.

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Section: Related Workmentioning

confidence: 99%

Containment and equivalence of well-designed SPARQL

Pichler

Skritek

2014

Proceedings of the 33rd ACM SIGMOD-SIGACT-SIGART Symposium on Principles of Database Systems

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“…Static analysis and optimisation of SPARQL queries has received significant attention in recent years [4,6,14,15,16]. A key ingredient for query optimisation is the availability of a comprehensive catalog of equivalence-preserving transformation rules for SPARQL patterns.…”

Section: Static Analysis and Optimisationmentioning

confidence: 99%

On the Semantics of SPARQL Queries with Optional Matching under Entailment Regimes

Kostylev

Grau

2014

The Semantic Web – ISWC 2014

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Abstract. We study the semantics of SPARQL queries with optional matching features under entailment regimes. We argue that the normative semantics may lead to answers that are in conflict with the intuitive meaning of optional matching, where unbound variables naturally represent unknown information. We propose an extension of the SPARQL algebra that addresses these issues and is compatible with any entailment regime satisfying the minimal requirements given in the normative specification. We then study the complexity of query evaluation and show that our extension comes at no cost for regimes with an entailment relation of reasonable complexity. Finally, we show that our semantics preserves the known properties of optional matching that are commonly exploited for static analysis and optimisation.

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“…In [27], the authors formalized the syntax and semantics of SPARQL, presenting the first step towards understanding the fundamental properties of this language. This work was followed by studies about the complexity of query evaluation [34,23,5,29], query optimisation [22,30,12,13], query federation [10], expressive power analysis [3,31,20], and provenance tracking [17,18]. The theoretical study of SPARQL has impacted the Semantic Web in several ways, influencing the standard definition of SPARQL by the W3C and also the form in which users query RDF.…”

Section: Introductionmentioning

confidence: 99%

Designing a Query Language for RDF

Arenas

Ugarte

2016

Proceedings of the 35th ACM SIGMOD-SIGACT-SIGAI Symposium on Principles of Database Systems

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When querying an RDF graph, a prominent feature is the possibility of extending the answer to a query with optional information. However, the definition of this feature in SPARQL -the standard RDF query language-has raised some important issues. Most notably, the use of this feature increases the complexity of the evaluation problem, and its closed-world semantics is in conflict with the underlying open-world semantics of RDF. Many approaches for fixing such problems have been proposed, being the most prominent the introduction of the semantic notion of weakly-monotone SPARQL query. Weakly-monotone SPARQL queries have shaped the class of queries that conform to the open-world semantics of RDF. Unfortunately, finding an effective way of restricting SPARQL to the fragment of weakly-monotone queries has proven to be an elusive problem. In practice, the most widely adopted fragment for writing SPARQL queries is based on the syntactic notion of well designedness. This notion has proven to be a good approach for writing SPARQL queries, but its expressive power has yet to be fully understood.The starting point of this paper is to understand the relation between well-designed queries and the semantic notion of weak monotonicity. It is known that every well-designed SPARQL query is weakly monotone; as our first contribution we prove that the converse does not hold, even if an extension of this notion based on the use of disjunction is considered. Given this negative result, we embark on the task of defining syntactic fragments that are weaklymonotone, and have higher expressive power than the fragment of well-designed queries. To this end, we move to a more general scenario where infinite RDF graphs are also allowed, so that interpolation techniques studied for first-order logic can be applied. With the use of these techniques, we are able to define a new operator for SPARQL that gives rise to a query language with the desired properties (over finite and infinite RDF graphs). It should be noticed that every query in this fragment is weakly monotone if we restrict to the case of finite RDF graphs. Moreover, we use this result to provide a simple characterization of the class of monotone CONSTRUCT queries, that is, the class of SPARQL queries that produce RDF graphs as output. Finally, we pinpoint the complex-

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SPARQL Query Containment under RDFS Entailment Regime

Cited by 29 publications

References 13 publications

Containment and equivalence of well-designed SPARQL

Containment and equivalence of well-designed SPARQL

On the Semantics of SPARQL Queries with Optional Matching under Entailment Regimes

Designing a Query Language for RDF

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