A conceptual domain may be associated with either a data element concept or a value domain. A conceptual domain is not a mandatory association, and there may be a one-to-many relationship between a data element concept and a conceptual domain, or a value domain and a conceptual domain.

Countries of the world can be expressed as a conceptual domain. The concept of countries can be measured by both enumerated and non-enumerated value domains. An enumerated value domain may reference the Australian Standard Classification of Countries (2011) and provide a four digit code (i.e. NNNN). A non-enumerated value domain may still reference the same classification, but collect country names using a textual field instead (i.e Text X[X(99)]. Both the enumerated and non-enumerated value domains could be associated with the conceptual domain for countries. The conceptual domain might also be associated with several data element concepts which incorporate country as a central theme, such as Person —country of birth, Person — country of residence, or Person — country of citizenship.

ISO/IEC 11179-3 Section 11.3.2.1

Conceptual_Domain is a class, each instance of which models a conceptual domain (3.2.21), a set of value meanings (3.2.141) which may either be enumerated or expressed via a description. Conceptual_Domain is an abstract class, which has two possible subclasses: Enumerated_Conceptual_Domain (11.3.2.2) and Described Conceptual_Domain (11.3.2.4). Every Conceptual_Domain instance must be either an Enumerated_Conceptual_Domain or a Described Conceptual_Domain or a combination of the two.