XML-RPC | blogatom.

Via Sam RubySimon FellCharles Cook:

The very informal API specs that XML-RPC seems to attract are often wrong, or misunderstood so that the server implement something different. Businesses are using XML-RPC for serious purposes and this potential for confusion wastes time and money.

I agree. DW would probably say the XML-RPC spec family is “flexible”, I say they are sloppy. I think I’m going to stick with W3C specs whenever possible.