A HTTP request is a function call. A function call is message passing. No matter if you use RPC, SOAP or what not. It's conceptually all the same - the caller sends a message to the callee which responds with another message.
Yes, if you map the concepts over. Which is what you just did. The RESTful architecture is explicitly _not_about function calls. It's about manipulating state diagrams. Yes, you do that through a message, but it's different than a function call, unless you define 'function' and 'message' in a way that's completely meaningless. If any message is a function call, a UDP packet is a function call.
