Procedure
The selected link has no definition.
Possible causes:
1. The source node or target node of the link is not an entity type,but a data model. In this case, the link is simply a graphicalcompression of the relationships involved and has not separatedefinition. To display the entity types and their relationships,first select the data model and select Edit -> Expand.
2. The link is a relationship where source entity type and targetentity type are identical.