Instance specifications in UML

In UML models, instance specifications are elements that represent an instance in the modeled system. When you instantiate a classifier in a model, the instance specification that you create represents an entity in the modeled system at a point in time, similar to a snapshot of the entity. You can model changes to the entity over time by creating several instance specifications, one for each snapshot.

Instance specifications can include the following information about the entity:

Like classifiers, instance specifications have attributes that are referred to as slots. An instance specification can have one slot for each structural feature of its classifier, including inherited features. You can specify values for each slot in an instance specification as long as a valid type is defined for the slot.

The following figure shows a class named Member. The class has two attributes, ID and Name. The ID attribute is of type Integer and the Name attribute is of type UnlimitedNatural.

The following figure shows the corresponding instance specification that has two slots and values. The value of the ID slot is 1, and the value of the Name slot is John Q Public.


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