Object diagram#Instance specifications

One feature specification (English InstanceSpecification ) is a model element in the Unified Modeling Language ( UML), a modeling language for software and other systems.

Description

One feature specification specifies a concrete entity in a modeled system. It specifies selected aspects of this entity, especially what the name of this and of which it is an expression classifier or instance. Further, it can declare a specific value for each structural feature of the classifier. The name of a structural feature, combined with a concrete value refers to the UML2 as a slot.

Expression specification can be used very flexibly. For example, a modeler does not necessarily specify a name. Further, the specification expression may be associated with zero or more classifiers.

The graphical representation of a specification expression differs only in details from that of a class. First, the name of the expression followed by a colon and the name of the classifier of which the expression is an instance. This text is always underlined. Second, the slots are specified in the form name = value in an area of the enclosing rectangle.

The second illustration shows an occurrence specification for an anonymous expression. This example also shows that in addition to the name and value of a slot whose type can also be listed in the graphical notation.

Expression specification and associations

From an association, it may also give as manifestations of a class, for both are specializations of Classifier. The expression of an association is called object relation or link. The graphical notation for a link largely corresponds to the graphical notation for an association. The figure at right shows an occurrence specification for an object relationship between two versions of the classifier person.

Differences to the UML 1.4

Neither the model nor the Object element model element link from the UML 1.4 was adopted into the UML2. Both were replaced by expression specification.