I'm beginning to see what all this XML (eXtensible Markup Language)-RPC (Remote Procedure Call) is all about. It's a more formal specification of the WWW (World Wide Web) CGI (Common Gateway Interface) because I guess reading the HTML (HyperText Markup Language) source and finding out the input fields for a form, then URL (Uniform Resource Locator)encode the data to call the external program is just too much work for some people.
I've done work before, [1] using, I guess, a form of CGI-RPC to implement a program that does an Internet search using the major search engines to gather the results. And yes, it's was (and still is to a degree) a pain because each engine basically has a different calling convention (or API (Application Program Interface) if you will). XML-RPC seems to be a way to standardize on an API, such as a search engine API.
Not that it's a bad idea, but XML seems a bit overbloated for me. But I guess for the type of services being done, like the Blogger API [2] it's not that bad of overhead. And just think, if I can implement the Blogger XML-RPC API, not only can I claim alphabet-soup compliancy, but I can use several tools to write my blogger with, not just using a web form or email.
[1] http://www.conman.org/people/spc/refs/search/