Here's UserLand's Winer talking at Infoworld's Conference on web services. He has some good points to make but then we get the old hobby horse. Pointing at IBM and Microsoft, Winer said WSDL (Web Services Description Language) was invented in such a way that it will only work in Java and .Net environments. "It can't work in a dynamic environment; it's a static interface," he said.

I have to say, I just don't get this. WSDL is a formalised documentation of a SOAP interface and the end points and locations at which that service is located. Because WSDL is XML it can be mostly generated directly from web service code in some environments. It can also be read and used to generate code and function stubs for a client to call it. I can't see anything to stop a web service written in a scripted environment like Perl, PHP, VB or UserLand's scripting language being documented in WSDL, even if it's done by hand. in fact Simon Fell has done exactly this for UserLand's Manila SOAP interface.

Looking from the client end, I can't see anything inherent in a scripting language that would stop you writing something to parse a WSDL file, extract the key information and build function calls. More likely in both scripted and compiled languages is that you'd define a system that understood the function calls after reading the WSDL. You'd then only use the WSDL at run time to determine the location of the end points. This mainly due to the difficulties in understanding the semantics of the function calls. This is mostly because (for example) knowing that PostID is an Int doesn't tell you where the data comes from or why you should use it.

Our Dave keeps making these statements about WSDL being unsuitable for dynamic environments but he doesn't seem to be able to say why. I've just spent the last few minutes searching for an example of this in a mailing list late last year, but failed. If I find it again, I'll post it. Ah! Google to the rescue. Start here and follow the thread.


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[ 18-Jan-02 3:45pm ]