“…It describes concepts and relationships among them, it can be defined as a 4-tuple: σ =< C, R, I , A >,where C is a set of classes (or concepts), R is a set of taxonomic and non-taxonomic relations, I is a set of individuals and A is a set of axioms (Gruber, 1993). Ontology-based semantic technologies are about the activities, theories and principles governing the domain, they can assist in managing, standardizing and integrating heterogeneous information (Fernández-López et al, 1997;El Bassiti & Ajhoun, 2014). In the following parts, we reviewed (1) ontology engineering and its methodologies; (2) ontology learning (OL); and (3) ontology validation approaches.…”