The schema defines some types used globally by the system, for instance in Web service WSDL's, in results etc. The tag wraps the incoming message of a service call. It is indispensable in the cases when the result is of mixed content. It also an implementation of a communication protocol between Web service and a service call, i.e. a Web service can return a message which is 'result' marked as 'STREAM' or 'END_OF_STREAM' and the service call will be stay active or terminate respectively, because it passes the result to its local RECEIVE Web service. Basically everything that is returned to a service call is wrapped (if the Web service did not do that) into this tag and passed to the respective RECEIVE which decides what to do. For instance, RECEIVE may update the ids. Used to mark the result arrival time A Web service can mark a a result and a peer's RECEIVE will deal with it. The number of results sent by a stream. the position of a message in a stream. The xs:IDREF type is not used on purpose. This tells which service call the node belongs as a result. This element is put into SOAP header on sending the request to the Web service. This way an ActiveXML-aware Web service can respond asynchronously. IMPORTANT: this actually mimics WS-Addressing, maybe it is a good idea to use it Address of a node (normally a service call node) in the system can be referenced by currentID or originalID.