Wednesday, December 26, 2007

My (unsubstantiated) Snapshot View of SOAP/WS-* and REST

At the moment, I haven't got the links to back me up, but I thought it's important to capture the thought before it escapes me.

I think SOAP/WS-* is an ambitious 100% vision for SOA that is 60% implemented.
And I think REST is a pragmatic 80% vision for SOA that is more than 90% implemented.

That model then explains to me the mutual contempt of both camps. The SOAP/WS-* group criticises REST for an overly simplistic model that does not cover a number of use cases - notably Quality of Service specification (security, reliability, transactions), policy-driven service interactions, process definition, exploitation of "industrial strength" message queue infrastructure, etc. That's because the SOAP/WS-* brief is all-encompassing. They've bitten off a lot.

The REST group criticises SOAP/WS-* for exactly that. They believe that SOAP/WS-* has bitten off more than it can chew. REST has taken a modest bite of the SOA problem, and has produced tangible results. What has SOAP/WS-* delivered except complexity?

A year ago, the winner of this argument would have been REST. But the SOAP/WS-* camp has been steadily chewing away at what they've bitten off. And delivering, bit by bit. Two words - Tango and WSO2. SOAP/WS-* complex? Vapourware? Not anymore.

Now it's the REST camp's turn to be defensive about their incompleteness of vision. We're beginning to hear mumblings about WADL, HTTPR and message-level security. I detect an air of defensiveness in talk about transactions and process definition. My long years of experience dealing with commercial vendors tells me that when someone questions the need for a capability, it usually means their product doesn't have it (yet). (Once they have the feature, it of course becomes indispensible and any rival product without it isn't serious competition.) Many of the RESTafarian arguments against the "unnecessary" features of SOAP/WS-* give me a feeling of déjà vu.

And oh, while REST is ahead of SOAP/WS-* on implementation, it's still not at 100%. Do let me know, for example, when PUT and DELETE are finally implemented by browsers. Ouch.

I'm not gloating that a bit of the REST smugness has been punctured (OK, just a little bit). I'm happy that the two worlds are improving their levels of maturity. In 2008, I'll be looking for REST to expand their vision, and for SOAP/WS-* to deliver on their vision.

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