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   Re: [xml-dev] Doing Web services right

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Mike Champion wrote:
> To be honest, this is something I'm having a hard time coming to grips 
> with.  The RESTifarians make a strong point that every WSDL file defines 
> a new "protocol", and that ordinary users can't be expected to grasp the 
> subtleties of protocol design.  Getting back to my original point, that 
> seems like saying that the specific message format that a CGI (or 
> ASP/JSP/etc.) backend expects is a "protocol."  True in the literal 
> sense of the word "protocol" in English, but I'm not sure it means 
> anything more than "the minimal expectation by the server of the 
> information content needed to do its job" (which is my understanding of 
> the position that folks including Walter Perry and Sean McGrath 
> advocate). 

Let's move past the abstract semantics and talk about concrete 
specifics. Basically all application protocols have a concept of 
"thing", a way of naming things and a way of requesting a representation 
of a thing be shipped over the network. FTP get, POP RETR, HTTP GET, 
Jabber Query etc. Because they all use a different syntax, I have to 
make a different user agent for each of them...even if my problem is 
restricted to "fetch me that data" (as it often is).

Similarly, basically every web service invents a new way of naming 
things, requesting representations of those things and shipping those 
things across the network. Web Service standards in general, and WSDL in 
particular refuse to standardize these concepts. Furthermore, WSDL makes 
it difficult to even use the existing Web standards for these things.

> ... It is VERY TRUE that the Web services industry has given 
> WSDL users immense lengths of rope with which they can hang themselves 
> by generating tightly-coupled, RPC-style code for both sides from the 
> WSDL file. 

It isn't that WSDL gives you the tools to hang yourself. It is that it 
refuses to give you the tools to build systems that use established 


Everybody is happy about the fact that SOAP allows access to Web 
features but has anybody actually tried to build a Web-like system in 
real SOAP toolkits using WSDL descriptions for them? How does one 
describe a Web of fetchable resource representations using WSDL?

  Paul Prescod


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