In description logics, concept names are regarded as atomic concepts, role names are regarded as atomic roles. In general, a concept denotes the set of individuals that belongs to it, and a role denotes a relationship between concepts.The syntax of a member of the description logic family is characterized by its recursive definition, in which the constructors that can be used to form concept terms are stated. Some common constructors include logical constructors in first-order logic such as intersection or conjunction of concepts, union or disjunction of concepts, negation or complement of concepts, value restriction (universal restriction), existential restriction, etc. Other constructors may also include restrictions on roles which are usual for binary relations, for example, inverse, transitivity, functionality, etc. Especially for intersection and union, description logics use the symbols and to distinguish them from the first-order logic and and or.
