QUALIFIABLE is used in a reference property where one or more key components of the referenced objects need not be taken from other properties in the referring object, but can be supplied in the property itself. It is used when all key data cannot be stored in properties of a referencing definition, but the name of the referenced definition must be qualified by the key property.

For example, the following KEYED (BY) clause states that the value of key_component_1 should be taken from property_name_1 and so the reference property would contain just the names of the reference objects.

However, this KEYED BY clause states that the value of key_component_1 should be taken from this property; that is, the one with this KEYED BY clause, and so the reference property could contain the values of both the names and the key_component_1s of the reference objects. Under these conditions, the values of the names are separated from the values of the key-component_1s by periods.