Browsing by Author "Perez, Jorge"

Now showing 1 - 6 of 6
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    An extension of SPARQL for RDFS
    (SPRINGER-VERLAG BERLIN, 2008) Arenas, Marcelo; Gutierrez, Claudio; Perez, Jorge; Christophides, V; Collard, M; Gutierrez, C
    RDF Schema (RDFS) extends RDF with a schema vocabulary with a predefined semantics. Evaluating queries which involve this vocabulary is challenging, and there is not yet consensus in the Semantic Web community on how to define a query language for RDFS. In this paper, we introduce a language for querying RDFS data. This language is obtained by extending SPARQL with nested regular expressions that allow to navigate through an RDF graph with RDFS vocabulary. This language is expressive enough to answer SPARQL queries involving RDFS vocabulary, by directly traversing the input graph.
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    Bidirectional Constraints for Exchanging Data: Beyond Monotone Queries
    (IJCAI-INT JOINT CONF ARTIF INTELL, 2015) Arenas, Marcelo; Dieguez, Gabriel; Perez, Jorge; Yang, Q; Wooldridge, M
    In this paper, we propose to use the language of bidirectional constraints to specify schema mappings in the context of data exchange. These constraints impose restrictions over both the source and the target data, and have the potential to minimize the ambiguity in the description of the target data to be materialized. We start by making a case for the usefulness of bidirectional constraints to give a meaningful closed-world semantics for st-tgds, which is motivated by Clark's predicate completion and Reiter's formalization of the closed-world assumption of a logical theory. We then formally study the use of bidirectional constraints in data exchange. In particular, we pinpoint the complexity of the existence-of-solutions and the query evaluation problems in several different scenarios, including in the latter case both monotone and nonmonotone queries.
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    Composition and Inversion of Schema Mappings
    (ASSOC COMPUTING MACHINERY, 2009) Arenas, Marcelo; Perez, Jorge; Reutter, Juan; Riveros, Cristian
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    nSPARQL: A Navigational Language for RDF
    (SPRINGER-VERLAG BERLIN, 2008) Perez, Jorge; Arenas, Marcelo; Gutierrez, Claudio; Sheth, A; Staab, S; Paolucci, M; Maynard, D; Finin, T; Krishnaprasad, T
    Navigational features have been largely recognized as fundamental for graph database query languages. This fact has motivated several authors to propose RDF query languages with navigational capabilities. In particular, we have argued in a previous paper that nested regular expressions are appropriate to navigate RDF data, and we have proposed the nSPARQL query language for RDF, that uses nested regular expressions as building blocks. In this paper, we study some of the fundamental properties of nSPARQL concerning expressiveness and complexity of evaluation. Regarding expressiveness, we show that nSPARQL is expressive enough to answer queries considering the semantics of the RDFS vocabulary by directly traversing the input graph. We also show that nesting is necessary to obtain this last result, and we study the expressiveness of the combination of nested regular expressions and SPARQL operators. Regarding complexity of evaluation, we prove that the evaluation of a nested regular expression E over an RDF graph G can be computed in time O(vertical bar G vertical bar . vertical bar E vertical bar).
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    Querying Semantic Data on the Web
    (ASSOC COMPUTING MACHINERY, 2012) Arenas, Marcelo; Gutierrez, Claudio; Miranker, Daniel P.; Perez, Jorge; Sequeda, Juan F.
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    Simple and Efficient Minimal RDFS
    (ELSEVIER, 2009) Munoz, Sergio; Perez, Jorge; Gutierrez, Claudio
    The original RDFS language design includes several features that hinder the task of developers and theoreticians. This paper has two main contributions in the direction of simplifying the language. First, it 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. Second, it introduces a minimalist deduction system over this fragment, which by avoiding certain rare cases, obtains a simple deductive system and a computationally efficient entailment checking. (C) 2009 Elsevier B.V. All rights reserved.