A subset definition in which the membership is represented by a set of rules specifying the conditions for inclusion.
- The SNOMED CT expression constraint language is the standard way to represent an intensional subset definition of a subset of SNOMED CT concepts.
- A row in a Query Specification Reference Set is the standard way to distribute an intensional subset definition of a subset of SNOMED CT concepts.
An example of an intensional subset definition is concepts that are types of respiratory disease characterized by edema. This is represented as follows in expression constraint language: < 19829001 |disorder of lung| : 116676008 |associated morphology| = 79654002 |edema|