Object diagram
Object diagrams show the relationships between instances of different classes.
Figure 10 shows a specific order with two order items.
The order, the two order items, and the two items are instances of the corresponding classes from Figure 1. Their relationships represent instances of the associations between these classes.
Instances of classes are also referred to as objects and instances of associations as links. However, all instances are technically of the UML type InstanceSpecification. UML 2 defines only one InstanceSpecification type for instances of all classifier types, whereas UML 1.4 defined a special instance type for each classifier type (e.g., Class -> Object, Association -> Link, AssociationClass -> LinkObject, Component -> ComponentInstance etc.).
Instances can optionally show their own name and/or the name of their class, separated by a colon. In this example, the order object and the two item objects show both their own names and the name of their class, while the two order item objects only show their class names.
The attribute values for the objects are of the UML type Slot. A Slot shows the name of an attribute of the class for the instance (for example, Order number) and the value that this attribute has for the instance (for example, 42). The link ends (for example, position) are also of the Slot type. However, as they are directly linked to their value, that is, the corresponding object, in the diagram, only the relevant attribute name is displayed in the diagram.