qualifier

A slot for an attribute or list of attributes on a binary association, in which the values of the attributes select a unique related object or a set of related objects from the entire set of objects related to an object by the association. It is an index on the traversal of an association.

See association class, association end.

Semantics

A binary association maps an object to a set of related objects. Sometimes it is desirable to select an object from the set by supplying a value that distinguishes the objects in the set. This value could be an attribute of the target class. In general, however, the selector value may be part of the association itself, an association attribute whose value is supplied by the creator when a new link ...

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