3.3.1.1 Per Messaging Object
Messaging objects are represented by the MessagingObject ADM type. The following abstract object elements are maintained by the client for each MessagingObject ADM type:
Client.MessagingObject.ForeignIdentifier: An XID structure, as specified in section 2.2.2.2, that identifies changes to objects in the local replica. For more details about foreign identifiers, see section 3.3.5.2.3.