By default, when you create and specify an item type in the hmc.xml, the PK will be displayed as the item's identifier. This may not always be appropriate, for example when referencing a user. To use another property as the displayed identifier, i.e the email, use the following construct:
<type>
.
.
.
<defaultreference mode="replace">
<itemlayout>
<attribute name="someOtherPropertyName"/>
</itemlayout>
</defaultreference>
</type>
