Link relationships in UML

In UML, a link relationship is an instance of an association or a communication path. While an association is a relationship between two classifiers, a link is a relationship between objects or instances of the classifiers or nodes.

A link relationship is also an instance of a communication path between two nodes. When you create an object diagram by instantiating the nodes in deployment diagram, the relationship between the node instances is represented by a link.

As the following figure illustrates, a link relationship is displayed in the diagram editor as a solid line between the objects. In this case, the link relationship connects two node instances.

The following figure shows an object diagram in which an instance of the Member class is connected to an instance of the Address class by a link relationship, which is an instance of the association between the classes.

Two class instances are connected by a link.