Specifically, the reader asked:
Do you think these changes will cut into MQ's market share in middleware messaging? I know that MQ is often used as a transport for Web Services. Do you think SOAP can compete in this space?
So, are MTOM and XOP the death knell for WebSphere MQ and similar products? Interesting question, but the comparison is apples and oranges. XOP and MTOM are about compression; message-oriented middleware (MOM) is about reliability.
The typical transport for Web services is HTTP, based on TCP/IP, which is generally regarded as an unreliable protocol. Why? Because when there are network problems, packets can get lost. To make it reliable, you need something like FTP that will detect and resend lost packets.
A more reliable transport is asynchronous messaging, such as JMS providers like WebSphere MQ. A messaging system provides exactly-once delivery semantics, meaning that a message can't get lost. Why? Because the messaging system will store the message at the sender's end and retry transmitting the message to the receiver's end until it suceeds. (See Basic Messaging Terminology.) That's exactly-once delivery.
Also see the Guaranteed Delivery pattern. As my co-author Gregor Hohpe likes to say: Reliability is relative. No networking transport is completely reliable. Even with guaranteed messaging, the disk might get full, or it might get hit by a meteorite--either way, messages are lost. Heck, even the ARPANET might not survive a nuclear attack. (Answers.com, Internet Gurus)
So a messaging system is used to make delivery of a SOAP message reliable, whereas XOP and MTOM compress it. HTTP can still loose an MTOM message, it will just waste less bandwidth doing so.