Cardinality
You can specify cardinality for relationships. Suppose you have a Business concept that connects to an Address concept by means of two relationships: has address and has shipping address’.
Suppose also that a Business may have multiple addresses and does indeed have at least one location address. However, there is a constraint that this business may only have one shipping address for all shipments.
For this example, you would set the Cardinality for the has address relationship to be min , 1.
The Cardinality for the shipping address relationship would be exact , 1.