Logical Data Modeling - Multiplicity


Multiplicity constrain the number of values that may be contained by a container (ie entity set)

The multiplicity specifies valid cardinalities of the collection it represents. (It denotes the possible cardinalities values of the collection)

The multiplicity is a constraint on the cardinality, which shall:

  • not be less than the lower bound
  • and not greater than the upper bound specified (unless the multiplicity is unlimited (ie *), in which case there is no constraint on the upper bound).


The properties applied to the collection of the container element.


  • lower bound
  • upper bound

Collection Type

  • order (ordered or not) - ie the elements can be inserted/retrieved in a specific order
  • unique (is unique or not) - ie does not allow duplicate

The collection type properties defines the type of collection.

isOrdered isUnique Collection Type
false true set
true true OrderedSet
false false Bag
true false Sequence


  • A Multiplicity that is not multivalued can represent at most a single value
  • Infinity upperbound symbol: *

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