A value domain provides a set of permissible values by which a Data Element can be implemented. Value domains can be enumerated (e.g. Total centimetres NNN) or non-enumerated (e.g. Sex code N).

The union of a specific value domain with a specific Data Element Concept creates a Data Element. For example the data element concept Person—body height can be implemented through union with the Total centimetres NNN value domain.

An expression of a Value Meaning allowed in a specific Value Domain

ISO/IEC 11179 allows for 2 different types of Value Domains - enumerated vs non-enumerated. The distinction between these is that an enumerated value domain is specified by a list of all its Value Meanings, while a non-enumerated value domain is specified by a description rather than a list of all Permissible Values.

• An example of a enumerated value domain would be a list of 10-year cohorts for recording a persons age:
  • A code of A coresponsing to 0-15 years
  • A code of B coresponsing to 15-30 years
  • A code of C coresponsing to 30-45 years
  • A code of D coresponsing to 45+ years
  Here, every possible value within the set has been explicitly enumerated.
• An example of a non-enumerated value domain would be an numeric range for recording a persons age, where the number could be any two digit number greater than zero. While there is an implied set of values, these have not been expressly enumerated.

ISO/IEC 11179-3 Section 11.3.2.5

Value_Domain is a class each instance of which models a value domain (3.2.140), a set of permissible values (3.2.96). A value domain provides representation, but has no implication as to the Data Element Concept (3.2.29) with which the values are associated, nor what the values mean.

A Value_Domain is an abstract class which is used to denote a collection of Permissible_Values associated with a Conceptual_Domain (11.3.2.1). A Value_Domain has two possible subclasses: an Enumerated_Value_Domain (11.3.2.6) and a Described_Value_Domain (11.3.2.8). A Value_Domain must be either one or both an Enumerated Valued or a Described_Value_Domain.

Example: 'ISO 3166 Codes for the representation of names of countries' describes seven distinct Value_Domains for the single Conceptual_Domain 'names of countries'. The seven Value_Domains are: 'short name in English', 'official name in English', 'short name in French', 'official name in French', 'alpha-2 code', 'alpha-3 code' and 'numeric code'.

ISO/IEC 11179-3 Section 11.3.2.6

Enumerated_Value_Domain is a class each instance of which models an enumerated value domain (3.2.61), a value domain (3.2.140) that is specified by a list of all its permissible values (3.2.96). The Enumerated_Value_Domain class is a concrete subclass of the abstract class Value_Domain.

ISO/IEC 11179-3 Section 11.3.2.8

Described_Value_Domain is a class each instance of which models a described value domain (3.2.49), a value domain (3.2.140) that is specified by a description or specification, such as a rule, a procedure, or a range (i.e. interval) , rather than as an explicit set of permissible values (3.2.96). It is a concrete subclass of the abstract class Value_Domain. As a subclass of Value_Domain, a Described_Value_Domain inherits the attributes and relationships of the former.