31 citations · 58 across the 8 of their papers we have counts for
8 papers
On matrices and -relations
Robert Brijder, Marc Gyssens, Jan Van den Bussche
We show that the matrix query language corresponds to a natural fragment of the positive relational algebra on -relations. The fragment is defined by introduc…
Comparing Downward Fragments of the Relational Calculus with Transitive Closure on Trees
Jelle Hellings, Marc Gyssens, Yuqing Wu +4
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…
Structural characterizations of the navigational expressiveness of relation algebras on a tree
George H. L. Fletcher, Marc Gyssens, Jan Paredaens +2
Given a document D in the form of an unordered node-labeled tree, we study the expressiveness on D of various basic fragments of XPath, the core navigational language on XML docume…
On the Conditional Independence Implication Problem: A Lattice-Theoretic Approach
Mathias Niepert, Dirk Van Gucht, Marc Gyssens
A lattice-theoretic framework is introduced that permits the study of the conditional independence (CI) implication problem relative to the class of discrete probability measures.…
Relative Expressive Power of Navigational Querying on Graphs
George H. L. Fletcher, Marc Gyssens, Dirk Leinders +5
Motivated by both established and new applications, we study navigational query languages for graphs (binary relations). The simplest language has only the two operators union and…
Similarity and bisimilarity notions appropriate for characterizing indistinguishability in fragments of the calculus of relations
George H. L. Fletcher, Marc Gyssens, Dirk Leinders +3
Motivated by applications in databases, this paper considers various fragments of the calculus of binary relations. The fragments are obtained by leaving out, or keeping in, some o…
On the Conditional Independence Implication Problem: A Lattice-Theoretic Approach
Mathias Niepert, Dirk Van Gucht, Marc Gyssens
A lattice-theoretic framework is introduced that permits the study of the conditional independence (CI) implication problem relative to the class of discrete probability measures.…
On Typechecking Top-Down XML Tranformations: Fixed Input or Output Schemas
Wim Martens, Frank Neven, Marc Gyssens
Typechecking consists of statically verifying whether the output of an XML transformation always conforms to an output type for documents satisfying a given input type. In this gen…