Daniel Berlinger's Archipelago: [Question. Why does SOAP seem to have so many incantations like dateCreated xsi:type="xsd:dateTime" (with the magic being "xsi" and "xsd")? How many of these do I have to learn before I can write a useful SOAP call on the back of a napkin? (No motive, just trying to learn).]
The answer to this question is one: technically only the SOAP Envelope namespace is required. My example used xsi and xsd only to make a true apples to apples comparison with XML-RPC. XML-RPC requires type information, SOAP does not. In fact, most vendors discourage or ignore it's use, and truth be told, only provide it because early versions of Apache SOAP required it.
But your question made it clear to me that there are people who are not SOAP developers who are interested in knowing just a wee bit more about how this all works. So I wrote what amounts to a prequel to the Busy Developers Guide to SOAP 1.1 entitled A Gentle Introduction to SOAP. Enjoy!