Unresolved references also occur if classes or fields are deleted when the diagram update policy is disabled or if actions performed outside diagrams that result in broken references. Unresolved references are shown in class diagrams with different adornment icons to indicate the potential sources of the unresolved references.
For example, a classifier or a relationship in a class diagram that has an unresolved reference (that is, the enterprise bean or Java class or interface that the diagram element represents cannot be found.) has a special unresolved view adornment to indicate that this classifier or relationship has an unresolved reference.
As the following figure illustrates, the circled "x" on the supplier side of the generalization relationship between ClassC3 and ClassC2 indicates that the relationship resides in ClassC3, but the supplier diagram element (ClassC2) is unresolved. The generalization relationship between ClassC2 and ClassC1 is adorned with a circled "x", which indicates that the Java extends relationship between ClassC2 and ClassC1 no longer exists.
