Dependency (UML)


In the Unified Modeling Language, a Dependency is a relationship that shows that an element, or set of elements, requires other model elements for their specification or implementation. The element is dependent upon the independent element, called the supplier. Two or more elements in this relationship are called tuples.
In the UML, this is indicated by a dashed line pointing from the dependent to the independent element. The arrow representing a Dependency specifies the direction of a relationship, not the direction of a process.

Standard predefined dependencies

- defined dependencies include :
A UML link is run-time relationship between instances of classifiers, while a dependency is a model-time relationship between definitions.
A typical uni-directional link requires the one instance to know about, and thus depend, upon the other, but this is not required. A uni-directional link only requires the possibility of navigation not dependency.
Likewise, a bi-directional link requires that both instances may traverse to each other, but this also does not require dependency.
However, after the traversal of the association, if some property of the target instance's definition is accessed, such as an operation or attribute, a dependency is created.