Looking at an SAP UM driver, I see that it generates FROM and TO values in the Entitlement value when assigning an Activity Group.

It seems likely these values of the Start and Expiration dates would come from the entitlement granter.

Looking at the EntitlementConfiguration object I see:

<parameter mandatory="true" name="AG" source="read-attr" source-name="OBJECTS:EXT_OBJ_ID"/>
<parameter mandatory="true" name="LSNAME" source="read-attr" source-name="DisplayName"/>
<parameter name="FROM" source="external" source-name="fromDate"/>
<parameter name="TO" source="external" source-name="toDate"/>

How does one use a source of external, and where do the values come from? The DTD is unclear on this.