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Francois Bry - One of the best experts on this subject based on the ideXlab platform.
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semantic web Query Languages
Encyclopedia of Database Systems, 2009Co-Authors: James Bailey, Francois Bry, Tim Furche, Sebastian SchaffertAbstract:DEFINITION A number of formalisms have been proposed for representing data and meta data on the Semantic Web. In particular, RDF, Topic Maps and OWL allow one to describe relationships between data items, such as concept hierarchies and relations between the concepts. A key requirement for the Semantic Web is integrated access to data represented in any of these formalisms, as well the ability to also access data in the formalisms of the “standard Web”, such as (X)HTML and XML. This data access is the objective of Semantic Web Query Languages. A wide range of Query Languages for the Semantic Web exist, ranging from i) pure “selection Languages” with only limited expressivity, to fully-fledged reasoning Languages, and ii) from Query Languages restricted to a certain data representation format, such as XML or RDF, to general purpose Languages that support multiple data representation formats and allow simultaneous Querying of data on both the standard and Semantic Web.
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four lessons in versatility or how Query Languages adapt to the web
Lecture Notes in Computer Science, 2009Co-Authors: Francois Bry, Tim Furche, Benedikt Linse, Alexander Pohl, Antonius Weinzierl, Olga YestekhinaAbstract:Exposing not only human-centered information, but machineprocessable data on the Web is one of the commonalities of recent Web trends. It has enabled a new kind of applications and businesses where the data is used in ways not foreseen by the data providers. Yet this exposition has fractured the Web into islands of data, each in different Web formats: Some providers choose XML, others RDF, again others JSON or OWL, for their data, even in similar domains. This fracturing stifles innovation as application builders have to cope not only with one Web stack (e.g., XML technology) but with several ones, each of considerable complexity. With Xcerpt we have developed a rule- and pattern based Query language that aims to give shield application builders from much of this complexity: In a single Query language XML and RDF data can be accessed, processed, combined, and re-published. Though the need for combined access to XML and RDF data has been recognized in previous work (including the W3C's GRDDL), our approach differs in four main aspects: (1) We provide a single language (rather than two separate or embedded Languages), thus minimizing the conceptual overhead of dealing with disparate data formats. (2) Both the declarative (logic-based) and the operational semantics are unified in that they apply for Querying XML and RDF in the same way. (3)We show that the resulting Query language can be implemented reusing traditional database technology, if desirable. Nevertheless, we also give a unified evaluation approach based on interval labelings of graphs that is at least as fast as existing approaches for tree-shaped XML data, yet provides linear time and space Querying also for many RDF graphs. We believe that Web Query Languages are the right tool for declarative data access in Web applications and that Xcerpt is a significant step towards a more convenient, yet highly efficient data access in a "Web of Data".
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web and semantic web Query Languages a survey
Lecture Notes in Computer Science, 2005Co-Authors: James Bailey, Francois Bry, Tim Furche, Sebastian SchaffertAbstract:A number of techniques have been developed to facilitate powerful data retrieval on the Web and Semantic Web. Three categories of Web Query Languages can be distinguished, according to the format of the data they can retrieve: XML, RDF and Topic Maps. This article introduces the spectrum of Languages falling into these categories and summarises their salient aspects. The Languages are introduced using common sample data and Query types. Key aspects of the Query Languages considered are stressed in a conclusion.
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Querying the web reconsidered design principles for versatile web Query Languages
International Journal on Semantic Web and Information Systems, 2005Co-Authors: Francois Bry, Tim Furche, Sebastian Schaffert, Christoph Koch, Liviu Badea, Sacha BergerAbstract:A decade of experience with research proposals as well as standardized Query Languages for the conventional Web and the recent emergence of Query Languages for the Semantic Web call for a reconsideration of design principles for Web and Semantic Web Query Languages. This chapter first argues that a new generation of versatile Web Query Languages is needed for solving the challenges posed by the changing Web: We call versatile those Query Languages able to cope with both Web and Semantic Web data expressed in any (Web or Semantic Web) markup language. This chapter further suggests that well-known referential transparency and novel answer-closedness are essential features of versatile Query Languages. Indeed, they allow queries to be considered like forms and answers like formfillings in the spirit of the Query-by-example paradigm. This chapter finally suggests that the decentralized and heterogeneous nature of the Web requires incomplete data specifications (or incomplete queries) and incomplete data selections (or incomplete answers); the form-like Query can be specified without precise knowledge of the queried data, and answers can be restricted to contain only an excerpt of the queried data.
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towards a multi calendar temporal type system for semantic web Query Languages
Lecture Notes in Computer Science, 2004Co-Authors: Francois Bry, Stephanie SprangerAbstract:Time is omnipresent on the (Semantic) Web. However, formalism like XML, XML Schema, RDF, OWL and (Semantic) Web Query Languages have, if any, only very limited notions of temporal data types and temporal theories built-in. Recently, the development of Web Services for temporal operations has begun. In this article, we describe a connection, possibly the first one, between such Web Services and Web formalisms: A proposal of a type system for temporal and calendric data, called multi-calendar temporal type system seamlessly integrated into a host (Query) language. The type system’s associated type checking methods are beyond the scope of this article. For proof-of-concept purposes, the Web and Semantic Web Query language Xcerpt has been chosen.
Sebastian Schaffert - One of the best experts on this subject based on the ideXlab platform.
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semantic web Query Languages
Encyclopedia of Database Systems, 2009Co-Authors: James Bailey, Francois Bry, Tim Furche, Sebastian SchaffertAbstract:DEFINITION A number of formalisms have been proposed for representing data and meta data on the Semantic Web. In particular, RDF, Topic Maps and OWL allow one to describe relationships between data items, such as concept hierarchies and relations between the concepts. A key requirement for the Semantic Web is integrated access to data represented in any of these formalisms, as well the ability to also access data in the formalisms of the “standard Web”, such as (X)HTML and XML. This data access is the objective of Semantic Web Query Languages. A wide range of Query Languages for the Semantic Web exist, ranging from i) pure “selection Languages” with only limited expressivity, to fully-fledged reasoning Languages, and ii) from Query Languages restricted to a certain data representation format, such as XML or RDF, to general purpose Languages that support multiple data representation formats and allow simultaneous Querying of data on both the standard and Semantic Web.
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web and semantic web Query Languages a survey
Lecture Notes in Computer Science, 2005Co-Authors: James Bailey, Francois Bry, Tim Furche, Sebastian SchaffertAbstract:A number of techniques have been developed to facilitate powerful data retrieval on the Web and Semantic Web. Three categories of Web Query Languages can be distinguished, according to the format of the data they can retrieve: XML, RDF and Topic Maps. This article introduces the spectrum of Languages falling into these categories and summarises their salient aspects. The Languages are introduced using common sample data and Query types. Key aspects of the Query Languages considered are stressed in a conclusion.
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Querying the web reconsidered design principles for versatile web Query Languages
International Journal on Semantic Web and Information Systems, 2005Co-Authors: Francois Bry, Tim Furche, Sebastian Schaffert, Christoph Koch, Liviu Badea, Sacha BergerAbstract:A decade of experience with research proposals as well as standardized Query Languages for the conventional Web and the recent emergence of Query Languages for the Semantic Web call for a reconsideration of design principles for Web and Semantic Web Query Languages. This chapter first argues that a new generation of versatile Web Query Languages is needed for solving the challenges posed by the changing Web: We call versatile those Query Languages able to cope with both Web and Semantic Web data expressed in any (Web or Semantic Web) markup language. This chapter further suggests that well-known referential transparency and novel answer-closedness are essential features of versatile Query Languages. Indeed, they allow queries to be considered like forms and answers like formfillings in the spirit of the Query-by-example paradigm. This chapter finally suggests that the decentralized and heterogeneous nature of the Web requires incomplete data specifications (or incomplete queries) and incomplete data selections (or incomplete answers); the form-like Query can be specified without precise knowledge of the queried data, and answers can be restricted to contain only an excerpt of the queried data.
Bart Kuijpers - One of the best experts on this subject based on the ideXlab platform.
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walk logic as a framework for path Query Languages on graph databases
International Conference on Database Theory, 2013Co-Authors: Jelle Hellings, Bart Kuijpers, Jan Van Den Bussche, Xiaowang ZhangAbstract:Motivated by the current interest in Languages for expressing path queries to graph databases, this paper proposes to investigate Walk Logic (WL): the extension of first-order logic on finite graphs with the possibility to explicitly quantify over walks. WL can serve as a unifying framework for path Query Languages. To support this claim, WL is compared in expressive power with various established Query Languages for graphs, such as first-order logic extended with reachability; the monadic second-order logic of graphs; hybrid computation tree logic; and regular path queries. WL also serves as a framework to investigate the following natural questions: Is quantifying over walks more powerful than quantifying over paths (walks without repeating nodes) only? Is quantifying over infinite walks more powerful than quantifying over finite walks only? WL model checking is decidable, but determining the precise complexity remains an open problem.
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trajectory databases data models uncertainty and complete Query Languages
Journal of Computer and System Sciences, 2010Co-Authors: Bart Kuijpers, Walied OthmanAbstract:Moving objects produce trajectories. We describe a data model for trajectories and trajectory samples and an efficient way of modeling uncertainty via beads for trajectory samples. We study transformations of the ambient space for which important physical properties of trajectories, such as speed, are invariant. We also determine which transformations preserve beads. We give conceptually easy first-order complete Query Languages and computationally complete Query Languages for trajectory databases, which allow to talk directly about speed and uncertainty in terms of beads. The queries expressible in these Languages are invariant under speed- and bead-preserving transformations.
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trajectory databases data models uncertainty and complete Query Languages
Lecture Notes in Computer Science, 2006Co-Authors: Bart Kuijpers, Walied OthmanAbstract:Moving objects produce trajectories. We describe a data model for trajectories and trajectory samples and an efficient way of modeling uncertainty via beads for trajectory samples. We study transformations for which important physical properties of trajectories, such as speed, are invariant. We also determine which transformations preserve beads. We give conceptually easy first-order complete Query Languages and computationally complete Query Languages for trajectory databases, which allow to talk directly about speed and beads. The queries expressible in these Languages are invariant under speed- and bead-preserving transformations.
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data models and Query Languages for spatial databases
Data and Knowledge Engineering, 1998Co-Authors: Jan Paredaens, Bart KuijpersAbstract:The main purpose of this paper is to investigate the characteristics that distinguish spatial databases systems from traditional ones. Hereto, we give an overview of some well-known data models and Query Languages of spatial database systems. We also investigate the concept of genericity, as introduced by Chandra and Harel for classical databases, for spatial databases. Paredaens, Van den Bussche and Van Gucht have shown that the concept of genericity breaks up in a hierarchy of genericity classes. In this respect, we classify data models and Query Languages according to the type of generic operations they are designed to support.
Tim Furche - One of the best experts on this subject based on the ideXlab platform.
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semantic web Query Languages
Encyclopedia of Database Systems, 2009Co-Authors: James Bailey, Francois Bry, Tim Furche, Sebastian SchaffertAbstract:DEFINITION A number of formalisms have been proposed for representing data and meta data on the Semantic Web. In particular, RDF, Topic Maps and OWL allow one to describe relationships between data items, such as concept hierarchies and relations between the concepts. A key requirement for the Semantic Web is integrated access to data represented in any of these formalisms, as well the ability to also access data in the formalisms of the “standard Web”, such as (X)HTML and XML. This data access is the objective of Semantic Web Query Languages. A wide range of Query Languages for the Semantic Web exist, ranging from i) pure “selection Languages” with only limited expressivity, to fully-fledged reasoning Languages, and ii) from Query Languages restricted to a certain data representation format, such as XML or RDF, to general purpose Languages that support multiple data representation formats and allow simultaneous Querying of data on both the standard and Semantic Web.
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four lessons in versatility or how Query Languages adapt to the web
Lecture Notes in Computer Science, 2009Co-Authors: Francois Bry, Tim Furche, Benedikt Linse, Alexander Pohl, Antonius Weinzierl, Olga YestekhinaAbstract:Exposing not only human-centered information, but machineprocessable data on the Web is one of the commonalities of recent Web trends. It has enabled a new kind of applications and businesses where the data is used in ways not foreseen by the data providers. Yet this exposition has fractured the Web into islands of data, each in different Web formats: Some providers choose XML, others RDF, again others JSON or OWL, for their data, even in similar domains. This fracturing stifles innovation as application builders have to cope not only with one Web stack (e.g., XML technology) but with several ones, each of considerable complexity. With Xcerpt we have developed a rule- and pattern based Query language that aims to give shield application builders from much of this complexity: In a single Query language XML and RDF data can be accessed, processed, combined, and re-published. Though the need for combined access to XML and RDF data has been recognized in previous work (including the W3C's GRDDL), our approach differs in four main aspects: (1) We provide a single language (rather than two separate or embedded Languages), thus minimizing the conceptual overhead of dealing with disparate data formats. (2) Both the declarative (logic-based) and the operational semantics are unified in that they apply for Querying XML and RDF in the same way. (3)We show that the resulting Query language can be implemented reusing traditional database technology, if desirable. Nevertheless, we also give a unified evaluation approach based on interval labelings of graphs that is at least as fast as existing approaches for tree-shaped XML data, yet provides linear time and space Querying also for many RDF graphs. We believe that Web Query Languages are the right tool for declarative data access in Web applications and that Xcerpt is a significant step towards a more convenient, yet highly efficient data access in a "Web of Data".
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web and semantic web Query Languages a survey
Lecture Notes in Computer Science, 2005Co-Authors: James Bailey, Francois Bry, Tim Furche, Sebastian SchaffertAbstract:A number of techniques have been developed to facilitate powerful data retrieval on the Web and Semantic Web. Three categories of Web Query Languages can be distinguished, according to the format of the data they can retrieve: XML, RDF and Topic Maps. This article introduces the spectrum of Languages falling into these categories and summarises their salient aspects. The Languages are introduced using common sample data and Query types. Key aspects of the Query Languages considered are stressed in a conclusion.
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Querying the web reconsidered design principles for versatile web Query Languages
International Journal on Semantic Web and Information Systems, 2005Co-Authors: Francois Bry, Tim Furche, Sebastian Schaffert, Christoph Koch, Liviu Badea, Sacha BergerAbstract:A decade of experience with research proposals as well as standardized Query Languages for the conventional Web and the recent emergence of Query Languages for the Semantic Web call for a reconsideration of design principles for Web and Semantic Web Query Languages. This chapter first argues that a new generation of versatile Web Query Languages is needed for solving the challenges posed by the changing Web: We call versatile those Query Languages able to cope with both Web and Semantic Web data expressed in any (Web or Semantic Web) markup language. This chapter further suggests that well-known referential transparency and novel answer-closedness are essential features of versatile Query Languages. Indeed, they allow queries to be considered like forms and answers like formfillings in the spirit of the Query-by-example paradigm. This chapter finally suggests that the decentralized and heterogeneous nature of the Web requires incomplete data specifications (or incomplete queries) and incomplete data selections (or incomplete answers); the form-like Query can be specified without precise knowledge of the queried data, and answers can be restricted to contain only an excerpt of the queried data.
Jan Van Den Bussche - One of the best experts on this subject based on the ideXlab platform.
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DBPL - Relative expressive power of downward fragments of navigational Query Languages on trees and chains
Proceedings of the 15th Symposium on Database Programming Languages - DBPL 2015, 2015Co-Authors: Jelle Hellings, Stijn Vansummeren, Dirk Van Gucht, Jan Van Den Bussche, Marc Gyssens, Yuqing Wu, George H L FletcherAbstract:Motivated by the continuing interest in the tree data model, we study the expressive power of downward fragments of navigational Query Languages on trees. The basic navigational Query language we consider expresses queries by building binary relations from the edge relations and the identity relation, using composition and union. We study the effects on the expressive power when we add transitive closure, projections, coprojections, intersection, and difference. We study expressiveness at the level of boolean queries and path queries, on labeled and unlabeled trees, and on labeled and unlabeled chains. In all these cases, we are able to present the complete Hasse diagram of relative expressiveness. In particular, we were able to decide, for each fragment of the navigational Query Languages that we study, whether it is closed under difference and intersection when applied on trees.
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The impact of transitive closure on the expressiveness of navigational Query Languages on unlabeled graphs
Annals of Mathematics and Artificial Intelligence, 2013Co-Authors: George H L Fletcher, Dirk Leinders, Stijn Vansummeren, Dirk Van Gucht, Jan Van Den Bussche, Marc Gyssens, Yuqing WuAbstract:Several established and novel applications motivate us to study the expressive power of navigational Query Languages on graphs, which represent binary relations. Our basic language has only the operators union and composition, together with the identity relation. Richer Languages can be obtained by adding other features such as other set operators, projection and coprojection, converse, and the diversity relation. In this paper, we show that, when evaluated at the level of boolean queries with an unlabeled input graph (i.e. a single relation), adding transitive closure to the Languages with coprojection adds expressive power, while this is not the case for the basic language to which none, one, or both of projection and the diversity relation are added. In combination with earlier work, these results yield a complete understanding of the impact of transitive closure on the Languages under consideration.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
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FoIKS - The impact of transitive closure on the boolean expressiveness of navigational Query Languages on graphs
Lecture Notes in Computer Science, 2012Co-Authors: George H L Fletcher, Dirk Leinders, Stijn Vansummeren, Dirk Van Gucht, Jan Van Den Bussche, Marc Gyssens, Yuqing WuAbstract:Several established and novel applications motivate us to study the expressive power of navigational Query Languages on graphs, which represent binary relations. Our basic language has only the operators union and composition, together with the identity relation. Richer Languages can be obtained by adding other features such as other set operators, projection and coprojection, converse, and the diversity relation. In this paper, we show that, when evaluated at the level of boolean queries with an unlabeled input graph (i.e., a single relation), adding transitive closure to the Languages with coprojection adds expressive power, while this is not the case for the basic language to which none, one, or both of projection and the diversity relation are added. In combination with earlier work [10], these results yield a complete understanding of the impact of transitive closure on the Languages under consideration.
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Abstract state machines and computationally complete Query Languages
Information & Computation, 2002Co-Authors: Andreas Blass, Yuri Gurevich, Jan Van Den BusscheAbstract:Abstract state machines (ASMs) form a relatively new computation model holding the promise that they can simulate any computational system in lockstep. In particular, an instance of the ASM model has recently been introduced for computing queries to relational databases. This model, to which we refer as the BGS model, provides a powerful Query language in which all computable queries can be expressed. In this paper, we show that when one is only interested in polynomial- time computations, BGS is strictly more powerful than both QL and whilenew, two well-known computationally complete Query Languages. We then show that when a language such as whilenew is extended with a duplicate elimination mechanism, polynomial-time simulations between the language and BGS become possible. Copyright 2002 Elsevier Science (USA).
