UML enables the specialization of properties defined by associations. Enterprise Architect enables this through the Specialize Associations option in the advanced section of the context menu for an association.
The following dialog displays, showing all associations between the two classes connected by the current association and their parents.
The left two columns define the source role of the current association, while the right two define the target role. With this you are able to select the relationships of each end of the properties listed. When a relationship is set then this is drawn at the corresponding end of the connector on any diagram it appears on.