1. A method of processing Message Transmission Optimization Mechanism (MTOM) messages by a set of message handlers, said method comprising: a MTOM handler receiving an inbound MTOM message which comprises a root extensible markup language-binary optimized packaging (XOP) document and at least one binary attachment referenced by said root XOP document, wherein said MTOM handler is a first message handler in said set of message handlers; determining a Web service program that said MTOM message is addressed to selecting a particular pipeline for processing said MTOM message based on said particular pipeline being associated with said Web service program; unpackaging said MTOM message by separating said at least one binary attachment from said root XOP document; processing said MTOM message by said particular pipeline; and passing said processed MTOM message to a next handler for said Web service program.