- From: <noah_mendelsohn@us.ibm.com>
- Date: Thu, 13 Feb 2003 10:04:09 -0500
- To: "David Orchard" <dorchard@bea.com>
- Cc: xml-dist-app@w3.org
David Orchard quotes an exchange with Roy Fielding: > DO: Can representations be transferred over protocols > other than http, say ftp? > > RF:Yes. Any shared memory by message passing system is > dealing in representations, though most are constrained > to a particular implementation. So FTP >can< transfer a representation, at least in Roy's usage. Here are the questions I would follow with: Q. Is every piece of data carried by FTP a representation? A (proposed by Noah): I think if we answer "yes", then we are greatly diluting the interesting characteristics of representation as defined in REST. So my preferred answer would be "no" I believe Roy states in his thesis that REST is not the only appropriate or useful model for distributed computation, just an interesting and important one. Thus, I think we need two different terms. One needs to be specific to REST, and to carry all the connotations that go with that. If necessary, we can have a broader one that refers to all load/store transfers. Confusing them is dangerous, IMO. I think that many SOAP activites will, for better or worse, fall outside of the REST model. I think these convey "representations" only in the trivial and uninteresting sense that all messages are conveying some sort of data. Unless you model the resources and constrain the protocol, as REST does, I see little value in adding a fancy name to the general case. I find it confusing to use the same name (representation) that has a rather specific connotation in REST. So, I would prefer to reserve the term "representation" to refer to a set of data (typically a MIME-typed stream) that conveys some aspect of the state of a named Resource (I think I'd prefer to restrict this specifically to resources identified by URIs, though clearly similar systems could be built in other ways), and only in the case where access to such resources is modeled using the structures of REST (which is not necessarily HTTP, but necessarily builds on a view of GET, PUT, POST of representations as the means of manipulating and accessing a resource.) I find the simultaneous use of the term resource in this narrow sense and in a broader (e.g. FTP of a named file) sense to be more confusing than helpful. If you buy this narrow definition, then I claim that SOAP does not in all cases transfer a representation. Neither, for that matter, does a typical HTTP GET message, though that surely conveys some bits of state that represent something or other at the sender. ------------------------------------------------------------------ Noah Mendelsohn Voice: 1-617-693-4036 IBM Corporation Fax: 1-617-693-8676 One Rogers Street Cambridge, MA 02142 ------------------------------------------------------------------
Received on Thursday, 13 February 2003 10:06:14 UTC