Modifying the Properties of a Relationship
You can use the Entity Relationship Diagrams list or the Properties window to modify the properties of a relationship. For example, you can modify the text that Siebel Tools displays at the end points of a relationship.
You cannot use the Entity Relationship Diagrams list or the Properties window to modify the type of relationship, such as modifying a one-to-one relationship to a one-to-many relationship. To modify the type of relationship, you delete the old relationship, and then move the new relationship from the ERD Palette to the canvas.