Stephan's List: REST vs. SOAP

Stefan’s List is an interesting effort to categorize some very good bloggers into REST, SOAP, and (um) “either” camps. I know a few people on both sides of the isle and I don’t think any of them are on some sort of web-oriented death march. I mainly think about how business intent is most effectively expressed in message payloads – something neither REST nor WS-* are really helping with (it’s semantics after all).

My friend Paul Downey (http://blog.whatfettle.com/) of British Telecom (erroneously placed in the “wrong” camp in an earlier version of Stefan’s List) put together a brilliant slide deck (pdf) that unambiguously (and literally) illustrates his point of view about WS-*. I’ve been meaning to steal from it for some time. BTW, Paul is chairing a W3C working group to advise toolkits about mapping language constructs to XML Schema constructs – something that will help both sides of the WS isle. I think Paul’s working group will enable more XML Schema constructs to be supported in the mainstream, which in turn increases the vocabulary I can employ to represent my business intent.

REST Doesn’t Obviate WS-*
There is a VERY large IT constituency that relies heavily on modeling non-functional requirements. Pioneers have the luxury of trying these things out and mitigating the shortcomings as they go. Obviously, current enterprises want to extend their architectural core concepts into more open realms. But they need to prove that service-level requirements are achievable and that non-functional aspects can be modeled using approved best practices.

WS-* has grown around those needs. The specs provide CYA support for the big IT shops. I sometimes get upset that WS-* is no longer simple or particularly exciting. But people are often compelled into multilateral infrastructures and to make their complex interactions interoperable. There’s apparently a lot of money in achieving that.

PS. For the record, I use REST and tunnel it through SOAP and/or WS-* where needed.