Multiplicity vs. Cardinality

Multiplicity used to be called Cardinality, before the Unified Modeling Language of became a new de facto standard for the semantics of information metamodels.
- [Ref. 1] Booch/Rumbaugh/Jacobsen/Rational Corp.
- [Ref. 2] Object Management Group Analysis & Design Task Force.

The rationale for the change of name was that the cardinality of each participating entity type/role is easily confused with the size of the relation itself:
- An N-ary relation is a set of N-tuples contained in the direct product of its N entity type/role components.

Multiplicity used to be called Cardinality, before the Unified Modeling Language of became a new de facto standard for the semantics of information metamodels.