Web Services
Here’s a gem on a little-used mailing list:
Everyone seems to be gushing about Microsoft’s Open Specification Promise. While any headway is good in the horrible landscape that is Intellectual Property, my initial reaction is that it — like most such vendor promises — is too little, too late.
When I joined Yahoo, one of the biggest adjustments I had to make was to their use of “Web Services”. There, that phrase means any kind of machine-to-machine communication using HTTP; SOAP isn’t assumed (or preferred).
Anne-Thomas Manes extolls the virtues of WS-*;
It’s become axiomatic in some circles — especially in WS-* land, as well as in many other uses of XML — that the preferred (or only) means of offering extensibility is through URI-based namespaces, along with a flag to tell consumers when an extension needs to be understood (a.k.a. mustUnderstand).
True to form, Don’s using his witty charm and good looks (such as they are ;) to shape discussion of a topic… in this case, REST, where he splits the RESTifarian world into two; “hi” and “lo.”
More and more people are getting turned on to the advantages of using REST as a higher-level abstraction for networked applications, often comparing it favourably to SOAP and Web services.
Some folks at IONA have written a paper entitled Where HTTP Fails SOAP. I had a chance to look at this before I got it published, and their conclusions make a lot of sense — if you accept the premise that SOAP (and Web services) is about integration with existing applications.
You can describe just about anything with sufficient precision in plain English, given enough words. In practice, this doesn’t happen; specialised fields — whether science, finance or art — develop specialised jargon as a shorthand for concepts that are well-understood in that field. It gives greater precision, easier flow of ideas, and yes, it raises the bar to entry for newcomers.
I don’t talk much about it here, but I’m honoured to be the Chair of the W3C Web Services Addressing Working Group. This is something of an experiment for the W3C, so I gave an update on its progress as part of a panel discussion at the Advisory Committee meeting a few weeks ago. I’d like to share some of what I presented there.
Werner makes an excellent point;
As I’m sure many others were, I was intrigued to see that Microsoft published their idea of an Introduction to the Web Services Architecture and Its Specifications the other week.
(Another instalment in “XML Heresies.”)
Way back when the XML Protocol Working Group started kicking around, Henrik and I had a long-running, low-level “discusssion” about whether SOAP was a protocol or a format.
To use WSDL to describe RESTful interactions, you need some way of accommodating generative resource identifiers. In a nutshell, this means some part of the URI is dynamic. For example, with HTTP I might describe an address book where someone named “Jones” has a corresponding entry URI;
I’ve talked before about describing RESTful Web resources, going as far as prototyping a new format. That work was predicated on the assumption that WSDL wasn’t adequate.
The XML Protocol Working Group (of which I’m a member) has released a first draft of XOP, XML-binary Optimised Packaging, and a revised draft of MTOM, the Message Transmission Optimisation Mechanism, that leverages XOP.
