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Semantics and Complexity of SPARQL
This paper addresses systematically the formal study of SPARQL, concentrating in its graph pattern facility, providing a compositional semantics, and proving there are normal forms, among others that the evaluation of SParQL patterns is PSPACE-complete. Expand
Semantics and complexity of SPARQL
This article identifies a large class of SPARQL patterns, defined by imposing a simple and natural syntactic restriction, where the query evaluation problem can be solved more efficiently and shows that the evaluation problem is coNP-complete for well-designed patterns. Expand
Simple and Efficient Minimal RDFS
This paper introduces a small fragment which, preserving the normative semantics and the core functionalities, avoids the complexities of the original specification, and captures the main semantic functionalities of RDFS. Expand
Querying semantic web data with SPARQL
Some of the main results about the theory of RDF and SPARQL are surveyed putting emphasis on some research opportunities for the database community. Expand
Minimal Deductive Systems for RDF
This paper presents a minimalist program for RDF, by showing how one can do without several predicates and keywords of the RDF Schema vocabulary, obtaining a simpler language which preserves theExpand
Counting beyond a Yottabyte, or how SPARQL 1.1 property paths will prevent adoption of the standard
It is shown that any implementation that adheres to the SPARQL 1.1 specification is doomed to show the same behavior, the key issue being the need for counting solutions imposed by the current specification. Expand
Foundations of Semantic Web databases
This paper addresses the challenge of developing an abstract model and query language suitable to formalize and prove properties about the RDF data and querylanguage by studying theRDF data model, minimal and maximal representations, as well as normal forms. Expand
On the Semantics of SPARQL
This chapter gives a detailed description of the semantics of this language, a query language called SPARQL, including all the features in the specification by the W3C such as blank nodes in graph patterns and bag semantics for solutions. Expand
nSPARQL: A navigational language for RDF
This paper proposes the query language nSPARQL that uses nested regular expressions to navigate RDF data and proves that given an RDF graph G and a nested regular expression E, this problem can be solved in time O(|G|@?|E|). Expand
Static analysis and optimization of semantic web queries
This paper proposes a tree representation for SPARQL queries, called pattern trees, which captures the class of well-designed SParQL graph patterns and which can be considered as a query execution plan, and proposes several transformation rules for pattern trees. Expand