We present Ontop, an open-source Ontology-Based Data Access (OBDA) system that allows
for querying relational data sources through a conceptual representation of the domain of …

Motivated by the ongoing success of Linked Data and the growing amount of semantic data
sources available on the Web, new challenges to query processing are emerging …

Data federation addresses the problem of uniformly accessing multiple, possibly
heterogeneous data sources, by map** them into a unified schema, such as an RDF …

Abstract Cloud Computing and Service Oriented Architectures have seen a dramatic
increase of the amount of applications, services, management platforms, data, etc. gaining …

RDF Database Systems is a cutting-edge guide that distills everything you need to know to
effectively use or design an RDF database. This book starts with the basics of linked open …

Processing SPARQL queries involves the construction of an efficient query plan to guide
query execution. Alternative plans can vary in the resources and the amount of time that they …

Abstract The Linked Open Data (LOD) cloud is rapidly becoming the largest interconnected
source of structured data on diverse domains. The potential of the LOD cloud is enormous …

One of the major obstacles that currently prevents the Semantic Web from exploiting its full
potential is that the data it provides access to is sometimes not available or outdated. The …

Data retrieval systems are facing a paradigm shift due to the proliferation of specialized data
storage engines (SQL, NoSQL, Column Stores, MapReduce, Data Stream, and Graph) …

Access to hundreds of knowledge bases has been made available on the Web through
public SPARQL endpoints. Unfortunately, few endpoints publish descriptions of their content …