Substrate

- The superset of members to which an intensional subset definition is applied

- E.g. a specified version of a SNOMED CT edition

Intensional definition

- The set of rules (query) that defines whether a member of the substrate is included in the subset

- E.g. a SNOMED CT Expression Constraint

Expansion

- The result of applying an intensional definition to a given substrate

- E.g. concepts in specified version of the edition that comply with the constraint