This is the Dn — the fully distinguished name, i.e. the complete slash-delimited path in the UCS management information tree that uniquely locates a record describing one external application that has registered with this UCS domain's extpol registry. Because that external app can otherwise only be identified by its position in the object tree, this Dn is what you match against when a fault, event, or SNMP trap needs to be traced back to the exact one that raised it. A typical value might look like 'sys/extpol-reg/app-UCS-Central-01', pinpointing exactly which one under which parent object.