The Unified Modeling Language User Guide SECOND EDITION [Electronic resources] نسخه متنی

Chapter 13. Instances

In this chapter

• Instances and objects

• Modeling concrete instances

• Modeling prototypical instances

• The real and conceptual world of instances

The terms "instance" and "object" are largely synonymous, so, for the most part, they may be used interchangeably. An instance is a concrete manifestation of an abstraction to which a set of operations may be applied and which may have a state that stores the effects of the operation.

You use instances to model concrete things that live in the real world. Almost every building block in the UML participates in this class/object dichotomy. For example, you can have use cases and use case instances, nodes and node instances, associations and association instances, and so on.