You may want a repository item property to require a unique value. For example, you probably want each user profile to contain a login property that is unique to that profile and not shared by any other. You can mark a property as unique using the <attribute> tag, as in the following example:
<property name="login" data-type="string" required="true">
<attribute name="unique" value="true"/>
</property>
Repository editors in the ATG Control Center enforce the requirement that the value be unique.
