1. In a communication system having a service implemented by a processor on a services host device adapted to execute defined operations and extended operations and a client implemented by a processor on a client host device adapted to request execution by the service of defined operations and extended operations, a method performed by the client for invoking at least one of the extended operations, comprising the steps of: transmitting by the client to the service an extended operation invocation request identifying the at least one extended operation; and receiving by the client from the service in response to the invocation request an extended operation invocation response having a result obtained through execution by the service of the at least one extended operation, wherein the invocation request is a SOAP message that utilizes a SOAP method reserved for extended operation requests, and wherein the invocation response is a SOAP message that utilizes a SOAP method reserved for extended operation responses; wherein the invocation request and the invocation response each comprise a transaction identifier that uniquely identifies a transaction between the client and the service; and transmitting by the client to the service an extended operation status request having the transaction identifier and receiving by the client from the service in response to the extended operation status request an extended operation status response reporting operational status of the transaction, wherein the extended operation status request is a SOAP message that utilizes the SOAP method reserved for extended operation requests, and wherein the extended operation status response is a SOAP message that utilizes the SOAP method reserved for extended operation responses.