for the val attribute with a value of 0. The second object is named v2, is of class IndependentVariable, plays the NMinus1 role, and has val = 1. The DependentVariable object is named v3, and plays the N role. The topmost instance, an anonymous instance specification, has FibonacciFunction as its classifier, and may have an instance name, a role, and slots, but these are not shown here. The diagram also includes three named links, shown as lines. Links are instances of an association. In the second diagram, at a slightly later point in time, the IndependentVariable and DependentVariable objects are the same, but the slots for the val attribute have different values. The role names are not shown here. In the last object diagram, a still later snapshot, the same three objects are involved. Their slots have different values. The instance and role names are not shown here. Usage If you are using a UML modeling tool, you will typically draw object diagrams using some other diagram type, such as on a class diagram. An object instance may be called an instance specification or just an instance. A link between instances is generally referred to as a link. Other UML entities, such as an aggregation or composition symbol (a diamond) may also appear on an object diagram. References External links General information on UML including the official UML 2.0 specification. See especially the section on InstanceSpecification. The Expressive Power of Object Diagrams, an illustration from the real world Modal object diagrams, an extension of object diagrams with existential/universal and positive/negative modes. Unified Modeling Language diagrams