>I've constructed an automated procedure to gather information from a paid web service provider.
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>I built and tested it, and released it to the client. A month or two later, it broke (the client reported "incorrect number of parameters"). It turns out the Web Service provider had added a couple of parameters to the Web Service function call and VFP wouldn't proceed (I presume it was because the WSDL didn't match the code).
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>Well, I whined to the provider, and updated my code to match their new parameter list.
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>Now it's another month or two later and I'm getting the same error again. I suspect they have changed their parameters again.
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>I'm presuming that DotNet is less rigorous about new parameters if they are optional - is this the case with most other SOAP consumer languages? Is there something I'm doing wrong in VFP which causes this problem? Is VFP unique in this regard?
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>... or is the service provider simply managing their changes improperly? I seem to recall from a MS training event that when changes are needed to a working web service, you create a new function call and keep the original one running to keep current customers working...

AFAIK, in Web Service, parameters are not optional. The only optional parameter approach I have seen is when a Web Service method calls an internal method. In that case, the optional approach might be used. So, the provider has to consider that by advising its clients when such change occurs.