Abstract Information systems have to deal with an increasing amount of data that is
heterogeneous, unstructured, or incomplete. In order to align and complete data, systems …

Abstract ℰ ℒ EL is a simple tractable Description Logic that features conjunctions and
existential restrictions. Due to its favorable computational properties and relevance to …

Ontology reasoning finds a relevant application in the so-called ontology-based data
access, where a classical extensional database (EDB) is enhanced by an ontology, in the …

The chase is a family of algorithms used in a number of data management tasks, such as
data exchange, answering queries under dependencies, query reformulation with …

While big data analytics is considered as one of the most important paths to competitive
advantage of today's enterprises, data scientists spend a comparatively large amount of time …

Recent years have seen an increasing interest in ontology-mediated query answering, in
which the semantic knowledge provided by an ontology is exploited when querying data …

Abstract Knowledge graphs such as Yago and Freebase have become a powerful asset for
enhancing search, and are being intensively used in both academia and industry. Many …

Answering conjunctive queries (CQs) over a set of facts extended with existential rules is a
prominent problem in knowledge representation and databases. This problem can be …

This chapter gives an extended introduction to the lightweight profiles OWL EL, OWL QL,
and OWL RL of the Web Ontology Language OWL. The three ontology language standards …

Background Many ontologies have been developed in biology and these ontologies
increasingly contain large volumes of formalized knowledge commonly expressed in the …