Object Diagram - Overview

Overview

In the Unified Modeling Language (UML) an object diagram focuses on some particular set of object instances and attributes, and the links between the instances. A correlated set of object diagrams provides insight into how an arbitrary view of a system is expected to evolve over time. In early UML specifications the object diagram is described as:

"An object diagram is a graph of instances, including objects and data values. A static object diagram is an instance of a class diagram; it shows a snapshot of the detailed state of a system at a point in time. The use of obect diagrams is fairly limited, namely to show examples of data structure."

The latest UML 2.4 specification doesn't provided any definition of the object diagram.

The object diagrams and class diagrams are close relate, and use almost identical notation. Both diagrams are meant to visualize static structure of a system. While the class diagram show classes the object diagram displays instances of classes' or objects. Object diagrams are more concrete than class diagrams. They are often used to provide examples, or act as test cases for the class diagrams. Only those aspects of a model that are of current interest need be shown on an object diagram.