A Knowledge Representation can be distinguished into two groups, logical- and non logical-based formalisms. The second group is much close to our human intuition. Therefore it is also easier to understand Semantic Networks, Frame-based or Rule-base Representations. The problem with this non-logical based formalism is that they do not have a consistent Semantics and therefore we cannot apply entailment and Reasoning on top of that. Vice versa on logical-based Formalism everything is based on First Order Logic and therefore one has Semantics and one has Syntax and also Entailment. Therefore one can do proper Reasoning on top of that. In the same way also the Description Logics as they are Fragments of First Order Logic and based on it. This is the reason we use Logic based-Formalism because there we have Entailment and explicit as well as consistent Semantics.