Dependency (UML)

A dependence relationship (English Dependency ) is a model element in the Unified Modeling Language ( UML), a modeling language for software and other systems.

Description

A dependency relationship in UML 2 is a directed relationship between a dependent (client ) and an independent member ( supplier ). Both endpoints can also consist of several dependent or independent elements.

Interdependency relationships and associations, there is a crucial difference: from dependence relations instances can not be created. If two classes connected by the association, are also two instances of these classes with an instance of the association, that is, associated with an object relationship. For dependency relationships there are no comparable consequences because of them no instances can be created.

Graphically, a dependency relationship is shown as a dashed line with an open arrowhead. The arrowhead is drawn at the independent element.

Types of dependency relationships

Use relationship

Using equation ( usage) indicates that the dependent element uses the independent element. A use relationship is decorated with the keyword « use ».

Abstraction relationship

If an element is an abstraction of another element, an abstraction relation ( Abstraction ) can be modeled between the two. In the general case is an abstraction relation on the keyword " abstract " recognizable. Special cases, however, depart from it. " Derive " indicates that the dependent can be derived from the independent element. " Trace " indicates that between the two model elements a dependency relationship which must be considered when changes in the independent element. If an element refines another element, for example by modeling additional details, a dependency relationship with the keyword can " refine " to point out.

Inclusion relationship

The inclusion relationship means that a use case involves the behavior of another use case, that is, that the already included use case is called when the dependent other one runs out. An inclusion relationship is decorated with the keyword « include».

Realization relationship

The realization of equation ( Realization ) and interfacing relationship ( InterfaceRealization ) are two further forms of abstraction relation. Here the independent element represents a specification and an implementation dependent for the same. Often modeled this relationship that a class implements an interface, a pattern that is common in models for object-oriented software.

The graphical notation for a realization relationship is different from the generic notation for a dependency relationship by the arrowhead is drawn as in the generalization than not filled, closed tip. Compare the example on the right.

Distribution relationship

The distribution relationship ( engl. deployment) modeled a relationship between an artifact and a node. It indicates that the artifact is delivered on the nodes and installed in a suitable manner. A distribution relationship is decorated with the keyword « deploy ».

The figure at right shows two distribution relationships between two artifacts and a node.