Unique (attribute of property)
The unique attribute prevents entering two items that have the same value in the property where uniqueness was specified.
<property name = NAME label = LABEL unique="unique" />
The unique attribute is useful when you want to differentiate two items entered by one of the entity‘s field, for example the last name of an employee.
<entity name="Employee" label="Employee"> ... <property name="lastName" label="Last name" unique="unique" /> ... </entity>
In this case you will prevent the case where two employees have the same name despite they work on different companies.