Rich Salz: Post with opaque URL is the same thing as POST to URL with some specific top-level SOAP body element. Ideally doesn't enter into it. :) They're the same thing. I guess that's true in the same sense that a donut and a coffee cup are topologically the same thing.
Paul Prescod: I can *easily* give you all of reliability, asynchronousness, browser-compatibility, browser-independence with *one protocol*. On some days I *almost* wish that Paul would cease all direct and indirect uses of SMTP.
Thankfully, both messages went through nodes that captured, retained, and assigned a URL. That's the essence of the SOAP Response Message Exchange Pattern which gives rise to numerous low tech solutions. Example: imagine checking a SOAP message into CVS. Updates to the message itself could then have an audit trail and be access controlled. Such messages could be made are accessible via viewcvs. By virtue of the regular structure of the response, who's description could be captured by a WSDL, such a message would be readily consumable by a wide range of statically and dynamically typed languages. The entire "application" would have been constructed by off the shelf parts, albeit with a bit of hand editing of the content.
Sure, updates could have been done via HTTP PUT and retrievals via HTTP POST; but such an application would not be as easy to construct or as widely used.