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George H. L. Fletcher - One of the best experts on this subject based on the ideXlab platform.

  • Comparing the expressiveness of downward fragments of the Relation algebra with transitive closure on trees
    Information Systems, 2020
    Co-Authors: Jelle Hellings, Marc Gyssens, Yuqing Wu, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, George H. L. Fletcher
    Abstract:

    Abstract Motivated by the continuing interest in the tree data model, we study the expressive power of downward navigational query languages on trees and chains. Basic navigational queries are built from the Identity Relation and edge Relations using composition and union. We study the effects on relative expressiveness when we add transitive closure, projections, coprojections, intersection, and difference; this for Boolean queries and path queries on labeled and unlabeled structures. In all cases, we present the complete Hasse diagram. In particular, we establish, for each query language fragment that we study on trees, whether it is closed under difference and intersection.

  • Comparing Downward Fragments of the Relational Calculus with Transitive Closure on Trees
    arXiv: Databases, 2018
    Co-Authors: Jelle Hellings, Marc Gyssens, Yuqing Wu, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, George H. L. Fletcher
    Abstract:

    Motivated by the continuing interest in the tree data model, we study the expressive power of downward navigational query languages on trees and chains. Basic navigational queries are built from the Identity Relation and edge Relations using composition and union. We study the effects on relative expressiveness when we add transitive closure, projections, coprojections, intersection, and difference; this for boolean queries and path queries on labeled and unlabeled structures. In all cases, we present the complete Hasse diagram. In particular, we establish, for each query language fragment that we study on trees, whether it is closed under difference and intersection.

  • 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, 2015
    Co-Authors: Jelle Hellings, Marc Gyssens, Yuqing Wu, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, George H. L. Fletcher
    Abstract:

    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.

  • The impact of transitive closure on the expressiveness of navigational query languages on unlabeled graphs
    Annals of Mathematics and Artificial Intelligence, 2013
    Co-Authors: George H. L. Fletcher, Marc Gyssens, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, Dirk Leinders, Yuqing Wu
    Abstract:

    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

  • FoIKS - The impact of transitive closure on the boolean expressiveness of navigational query languages on graphs
    Lecture Notes in Computer Science, 2012
    Co-Authors: George H. L. Fletcher, Marc Gyssens, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, Dirk Leinders, Yuqing Wu
    Abstract:

    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.

Yuqing Wu - One of the best experts on this subject based on the ideXlab platform.

  • Comparing the expressiveness of downward fragments of the Relation algebra with transitive closure on trees
    Information Systems, 2020
    Co-Authors: Jelle Hellings, Marc Gyssens, Yuqing Wu, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, George H. L. Fletcher
    Abstract:

    Abstract Motivated by the continuing interest in the tree data model, we study the expressive power of downward navigational query languages on trees and chains. Basic navigational queries are built from the Identity Relation and edge Relations using composition and union. We study the effects on relative expressiveness when we add transitive closure, projections, coprojections, intersection, and difference; this for Boolean queries and path queries on labeled and unlabeled structures. In all cases, we present the complete Hasse diagram. In particular, we establish, for each query language fragment that we study on trees, whether it is closed under difference and intersection.

  • Comparing Downward Fragments of the Relational Calculus with Transitive Closure on Trees
    arXiv: Databases, 2018
    Co-Authors: Jelle Hellings, Marc Gyssens, Yuqing Wu, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, George H. L. Fletcher
    Abstract:

    Motivated by the continuing interest in the tree data model, we study the expressive power of downward navigational query languages on trees and chains. Basic navigational queries are built from the Identity Relation and edge Relations using composition and union. We study the effects on relative expressiveness when we add transitive closure, projections, coprojections, intersection, and difference; this for boolean queries and path queries on labeled and unlabeled structures. In all cases, we present the complete Hasse diagram. In particular, we establish, for each query language fragment that we study on trees, whether it is closed under difference and intersection.

  • 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, 2015
    Co-Authors: Jelle Hellings, Marc Gyssens, Yuqing Wu, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, George H. L. Fletcher
    Abstract:

    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.

  • The impact of transitive closure on the expressiveness of navigational query languages on unlabeled graphs
    Annals of Mathematics and Artificial Intelligence, 2013
    Co-Authors: George H. L. Fletcher, Marc Gyssens, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, Dirk Leinders, Yuqing Wu
    Abstract:

    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

  • FoIKS - The impact of transitive closure on the boolean expressiveness of navigational query languages on graphs
    Lecture Notes in Computer Science, 2012
    Co-Authors: George H. L. Fletcher, Marc Gyssens, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, Dirk Leinders, Yuqing Wu
    Abstract:

    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.

Dirk Van Gucht - One of the best experts on this subject based on the ideXlab platform.

  • Comparing the expressiveness of downward fragments of the Relation algebra with transitive closure on trees
    Information Systems, 2020
    Co-Authors: Jelle Hellings, Marc Gyssens, Yuqing Wu, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, George H. L. Fletcher
    Abstract:

    Abstract Motivated by the continuing interest in the tree data model, we study the expressive power of downward navigational query languages on trees and chains. Basic navigational queries are built from the Identity Relation and edge Relations using composition and union. We study the effects on relative expressiveness when we add transitive closure, projections, coprojections, intersection, and difference; this for Boolean queries and path queries on labeled and unlabeled structures. In all cases, we present the complete Hasse diagram. In particular, we establish, for each query language fragment that we study on trees, whether it is closed under difference and intersection.

  • Comparing Downward Fragments of the Relational Calculus with Transitive Closure on Trees
    arXiv: Databases, 2018
    Co-Authors: Jelle Hellings, Marc Gyssens, Yuqing Wu, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, George H. L. Fletcher
    Abstract:

    Motivated by the continuing interest in the tree data model, we study the expressive power of downward navigational query languages on trees and chains. Basic navigational queries are built from the Identity Relation and edge Relations using composition and union. We study the effects on relative expressiveness when we add transitive closure, projections, coprojections, intersection, and difference; this for boolean queries and path queries on labeled and unlabeled structures. In all cases, we present the complete Hasse diagram. In particular, we establish, for each query language fragment that we study on trees, whether it is closed under difference and intersection.

  • LICS - The primitivity of operators in the algebra of binary Relations under conjunctions of containments
    2017 32nd Annual ACM IEEE Symposium on Logic in Computer Science (LICS), 2017
    Co-Authors: Dimitri Surinx, Jan Van Den Bussche, Dirk Van Gucht
    Abstract:

    The algebra of binary Relations provides union and composition as basic operators, with the empty set as neutral element for union and the Identity Relation as neutral element for composition. The basic algebra can be enriched with additional features. We consider the diversity Relation, the full Relation, intersection, set difference, projection, coprojection, converse, and transitive closure. It is customary to express boolean queries on binary Relational structures as finite conjunctions of containments. We investigate which features are primitive in this setting, in the sense that omitting the feature would allow strictly less boolean queries to be expressible. Our main result is that, modulo a finite list of elementary interdependencies among the features, every feature is indeed primitive.

  • 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, 2015
    Co-Authors: Jelle Hellings, Marc Gyssens, Yuqing Wu, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, George H. L. Fletcher
    Abstract:

    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.

  • The impact of transitive closure on the expressiveness of navigational query languages on unlabeled graphs
    Annals of Mathematics and Artificial Intelligence, 2013
    Co-Authors: George H. L. Fletcher, Marc Gyssens, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, Dirk Leinders, Yuqing Wu
    Abstract:

    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

Jan Van Den Bussche - One of the best experts on this subject based on the ideXlab platform.

  • Comparing the expressiveness of downward fragments of the Relation algebra with transitive closure on trees
    Information Systems, 2020
    Co-Authors: Jelle Hellings, Marc Gyssens, Yuqing Wu, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, George H. L. Fletcher
    Abstract:

    Abstract Motivated by the continuing interest in the tree data model, we study the expressive power of downward navigational query languages on trees and chains. Basic navigational queries are built from the Identity Relation and edge Relations using composition and union. We study the effects on relative expressiveness when we add transitive closure, projections, coprojections, intersection, and difference; this for Boolean queries and path queries on labeled and unlabeled structures. In all cases, we present the complete Hasse diagram. In particular, we establish, for each query language fragment that we study on trees, whether it is closed under difference and intersection.

  • Comparing Downward Fragments of the Relational Calculus with Transitive Closure on Trees
    arXiv: Databases, 2018
    Co-Authors: Jelle Hellings, Marc Gyssens, Yuqing Wu, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, George H. L. Fletcher
    Abstract:

    Motivated by the continuing interest in the tree data model, we study the expressive power of downward navigational query languages on trees and chains. Basic navigational queries are built from the Identity Relation and edge Relations using composition and union. We study the effects on relative expressiveness when we add transitive closure, projections, coprojections, intersection, and difference; this for boolean queries and path queries on labeled and unlabeled structures. In all cases, we present the complete Hasse diagram. In particular, we establish, for each query language fragment that we study on trees, whether it is closed under difference and intersection.

  • LICS - The primitivity of operators in the algebra of binary Relations under conjunctions of containments
    2017 32nd Annual ACM IEEE Symposium on Logic in Computer Science (LICS), 2017
    Co-Authors: Dimitri Surinx, Jan Van Den Bussche, Dirk Van Gucht
    Abstract:

    The algebra of binary Relations provides union and composition as basic operators, with the empty set as neutral element for union and the Identity Relation as neutral element for composition. The basic algebra can be enriched with additional features. We consider the diversity Relation, the full Relation, intersection, set difference, projection, coprojection, converse, and transitive closure. It is customary to express boolean queries on binary Relational structures as finite conjunctions of containments. We investigate which features are primitive in this setting, in the sense that omitting the feature would allow strictly less boolean queries to be expressible. Our main result is that, modulo a finite list of elementary interdependencies among the features, every feature is indeed primitive.

  • 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, 2015
    Co-Authors: Jelle Hellings, Marc Gyssens, Yuqing Wu, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, George H. L. Fletcher
    Abstract:

    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.

  • The impact of transitive closure on the expressiveness of navigational query languages on unlabeled graphs
    Annals of Mathematics and Artificial Intelligence, 2013
    Co-Authors: George H. L. Fletcher, Marc Gyssens, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, Dirk Leinders, Yuqing Wu
    Abstract:

    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

Marc Gyssens - One of the best experts on this subject based on the ideXlab platform.

  • Comparing the expressiveness of downward fragments of the Relation algebra with transitive closure on trees
    Information Systems, 2020
    Co-Authors: Jelle Hellings, Marc Gyssens, Yuqing Wu, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, George H. L. Fletcher
    Abstract:

    Abstract Motivated by the continuing interest in the tree data model, we study the expressive power of downward navigational query languages on trees and chains. Basic navigational queries are built from the Identity Relation and edge Relations using composition and union. We study the effects on relative expressiveness when we add transitive closure, projections, coprojections, intersection, and difference; this for Boolean queries and path queries on labeled and unlabeled structures. In all cases, we present the complete Hasse diagram. In particular, we establish, for each query language fragment that we study on trees, whether it is closed under difference and intersection.

  • Comparing Downward Fragments of the Relational Calculus with Transitive Closure on Trees
    arXiv: Databases, 2018
    Co-Authors: Jelle Hellings, Marc Gyssens, Yuqing Wu, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, George H. L. Fletcher
    Abstract:

    Motivated by the continuing interest in the tree data model, we study the expressive power of downward navigational query languages on trees and chains. Basic navigational queries are built from the Identity Relation and edge Relations using composition and union. We study the effects on relative expressiveness when we add transitive closure, projections, coprojections, intersection, and difference; this for boolean queries and path queries on labeled and unlabeled structures. In all cases, we present the complete Hasse diagram. In particular, we establish, for each query language fragment that we study on trees, whether it is closed under difference and intersection.

  • 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, 2015
    Co-Authors: Jelle Hellings, Marc Gyssens, Yuqing Wu, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, George H. L. Fletcher
    Abstract:

    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.

  • The impact of transitive closure on the expressiveness of navigational query languages on unlabeled graphs
    Annals of Mathematics and Artificial Intelligence, 2013
    Co-Authors: George H. L. Fletcher, Marc Gyssens, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, Dirk Leinders, Yuqing Wu
    Abstract:

    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

  • FoIKS - The impact of transitive closure on the boolean expressiveness of navigational query languages on graphs
    Lecture Notes in Computer Science, 2012
    Co-Authors: George H. L. Fletcher, Marc Gyssens, Dirk Van Gucht, Jan Van Den Bussche, Stijn Vansummeren, Dirk Leinders, Yuqing Wu
    Abstract:

    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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