Have you tried XML RPC, it is a web service implmentation, not on SOAP, but not less than that. Visit http://www.xmlrpc.com, for more info. For me its better than SOAP as we don’t have to use those namespaces. Just write a simple code (maybe of just 15-20KB) and you are ready with it. Unlike Web service using SOAP, you don’t have List of functions coming, unless you make a “Wrapper” function for them, and that is the only bad thing of it, IF server doesn’t have documenation you cannot check it from its XML itself.

But how often you find API Implmentation not documented. You must try this, and if you need simple standard you need to implmented this.