Sam thinks good thoughts about how to use RESTful SOAP as a Blogger API. Nice. But there’s an important issue with SOAP and PUT. Unlike POST, PUT means “store”, and as such its processing model doesn’t provide a hook into which an additional processing model (i.e. SOAP) can be introduced. An intermediary or message processor seeing a PUT request with a SOAP body, would be correct to treat the body as opaque data, and wouldn’t be required to follow the SOAP processing model.
This is why I’ve talked about the need for a new HTTP method I’m currently calling “SET”, whose semantics will be “process and store”, and will therefore allow for an additional processing model to be inserted.