In a database, cardinalities are the values used to indicate how many times at minimum and at maximum that one entity of a table can be related to an entity in another table. When the maximum is undefined, the “n” notation is used to indicate “many” without giving a specific number.
Cardinalities are set forth for an entity to each table. The cardinality of the above example reads as follows: a path contains at least 0 and at most n equipment. Equipment may not be owned by one path and one alone.
See also: Data models, Entity-Relationship (Model)