SW = Semantic Web

Gruber (1993) states that an ontology is an explicit specification of a conceptualization, which, in turn, corresponds to objects, concepts and other entities of a given area of interest with their relationships. Consequently, an ontology can be used to model the concepts of a knowledge domain and its relations as well as learning objects.

The retrieval of information contained in the SW graphs is performed through the query language for RDF data, called SPARQL. This language closely resembles SQL for relational databases, including clauses (select, from and where), query modifiers (order by and distinct), and logical and comparison operators.

SWRL (Semantic Web Rule Language) is a standard SW language for the implementation of rules that can be used in the inference of new knowledge by the logical layer. The proof layer uses the phases followed by reasoners to validate this inference process. Finally, the trust layer aims to ensure that inferred knowledge is reliable.