TABLE OF CONTENTS An object diagram depicts the static structure of an entity at a particular time using classifier instances and relationship instances. An entity is a classifier, for example, a system, subsystem, or class.
A classifier instance is a specific concept with a unique identity, a set of operations that apply to it, and a state. Objects, use-case instances, data values, component instances, node instances, and subsystem instances are specific types of classifier instances. The stereotype or list of stereotypes and properties of a classifier instance's classifier apply to the classifier instance.
An object is an instance of a class. A class defines the structural and behavioral characteristics of its objects. An object defines values for its structural features, attribute values and specific relationships or links, and shares the behavioral features of its class. The state of an object is defined by the values of the object's structural features, what an object knows. The behavior of an object is defined by the behavior of its class, what an object can do. The most crucial aspect of an object is that it has its own identity. No two objects are the same, even if they have the same values for their structural features.
An object is depicted as a solid-outline rectangle with two standard compartments separated by horizontal lines. The top name compartment is required and contains the object name followed by a colon followed by a comma-separated list of the object's class names fully underlined.
