There are times when you might want to explicitly set a property value rather than have the property derivation logic supply one. This is done by specifying an override-property attribute in the <derivation> tag:
<item-descriptor name="employee"> <property name="department" item-type="department"/> <property name="empSpendingLimit" data-type="int"/> <property name="spendingLimit"> <derivation override-property="empSpendingLimit"> <expression>department.spendingLimit</expression> </derivation> </property> </item-descriptor>
The above change specifies that if the empSpendingLimit property is not null then it is used as the value of the spendingLimit property, otherwise the spendingLimit property is derived as before. Using the override-property attribute lets you edit in a Repository Editor a property that would otherwise be derived from another property.
