. . . . "According to Studer, an ontology is a formal, explicit specification of a shared conceptualization [37]. In other words, an ontology is a set of concepts and relations used to describe and represent an area of concern. Currently, ontologies are represented using OWL-2 language, which is the recommendation of the World Wide Web Consortium (W3C) [43]. Other recommended technologies/languages in the semantic web field are: RDF, used for representing information in the form of a graph composed of triples [45]; RDF Schema (RDFS), which provides a vocabulary for creating a hierarchy of classes and properties [3]; SPARQL 1 , used to query RDF data [44]; and the Semantic Web Rule Language (SWRL 2), which is used for extending the OWL model with rule axioms [18]." . . . . "2019-11-12T12:34:11+01:00"^^ . .