Storing and indexing massive RDF datasets
The resource description framework (RDF for short) provides a flexible method for modeling
information on the Web [34, 40]. All data items in RDF are uniformly represented as triples of …
information on the Web [34, 40]. All data items in RDF are uniformly represented as triples of …
The exact complexity of the first-order logic definability problem
We study the definability problem for first-order logic, denoted by FO-Def. The input of FO-
Def is a relational database instance I and a relation R; the question to answer is whether …
Def is a relational database instance I and a relation R; the question to answer is whether …
Axiomatizing the logical core of XPath 2.0
The first aim of this paper is to present the logical core of XPath 2.0: a logically clean,
decidable fragment, which includes most navigational features of XPath 2.0 (complex …
decidable fragment, which includes most navigational features of XPath 2.0 (complex …
Model theory of XPath on data trees. Part I: Bisimulation and characterization
We investigate model theoretic properties of XPath with data (in) equality tests over the class
of data trees, ie, the class of trees where each node contains a label from a finite alphabet …
of data trees, ie, the class of trees where each node contains a label from a finite alphabet …
[HTML][HTML] Model theory of XPath on data trees. Part II: Binary bisimulation and definability
S Abriola, ME Descotte, S Figueira - Information and Computation, 2017 - Elsevier
We study the expressive power of the downward and vertical fragments of XPath equipped
with (in) equality tests over possibly infinite data trees. We introduce a suitable notion of …
with (in) equality tests over possibly infinite data trees. We introduce a suitable notion of …
Expressive Completeness of Two-Variable First-Order Logic with Counting for First-Order Logic Queries on Rooted Unranked Trees
J Hellings, M Gyssens… - 2023 38th Annual …, 2023 - ieeexplore.ieee.org
We consider the class of finite, rooted, unranked, unordered, node-labeled trees. Such trees
are represented as structures with only the parent-child relation, in addition to any number of …
are represented as structures with only the parent-child relation, in addition to any number of …
On the expressive power of the relational algebra on finite sets of relation pairs
GHL Fletcher, M Gyssens, J Paredaens… - … on Knowledge and …, 2008 - ieeexplore.ieee.org
We give a language-independent characterization of the expressive power of the relational
algebra on finite sets of source-target relation instance pairs. The associated decision …
algebra on finite sets of source-target relation instance pairs. The associated decision …
A methodology for coupling fragments of XPath with structural indexes for XML documents
We introduce a new methodology for coupling language-induced partitions and index-
induced partitions on XML documents that is aimed for the benefit of efficient evaluation of …
induced partitions on XML documents that is aimed for the benefit of efficient evaluation of …
[PDF][PDF] An algebra for basic graph patterns
GHL Fletcher - Proceedings of the Workshop on Logic in Databases, 2008 - Citeseer
Motivated by recent developments in the dataspaces, web, and personal information
management communities, we outline research directions on query processing for SPARQL …
management communities, we outline research directions on query processing for SPARQL …
The impact of transitive closure on the expressiveness of navigational query languages on unlabeled graphs
GHL Fletcher, M Gyssens, D Leinders… - Annals of Mathematics …, 2015 - Springer
Several established and novel applications motivate us to study the expressive power of
navigational query languages on graphs, which represent binary relations. Our basic …
navigational query languages on graphs, which represent binary relations. Our basic …