The FROMDEF and TODEF keywords specify which types the relationship comes from and goes to respectively. This is reflected in the diagram and the relationship is drawn from the FROMDEF type to the TODEF type.

When used in a DEFINITION block, this is supporting a SINGLE relationship through the definition type. If you need to support more than one relationship through a definition type, a different keyword structure can be used to add them. For a definition of the new structure, see REPRESENTS EXPLICIT RELATIONSHIP.