Modeling element that connects classes
Introduction to the notion
The link (between objects) is the instantiation of an association (between classes). UML notation enables several constituent elements of the model to be written, all of great value, both for the quality of expression of the semantic model and its future use. These elements are:
- the name of the association (in theory, a binary association could have two names, according to the direction that it is read in);
- the cardinalities (on each “connector” of the association);
- the role names (ditto);
- an associative class, when it is necessary for the object to correspond to each link (reified association);
- one or more qualifiers, in the case of the qualified association.
Semantic modeling takes only a rare interest in the direction of an association (direction of navigation). Indeed, to direct an association means restricting the navigation of the model, prohibiting the “passage” from one class to another. Such restrictions are rarely within the domain itself.