- From: Daniel W. Connolly <connolly@beach.w3.org>
- Date: Thu, 31 Oct 1996 15:30:15 -0400
- To: Larry Masinter <masinter@parc.xerox.com>
- cc: yarong@microsoft.com, ejw@rome.ics.uci.edu, w3c-dist-auth@w3.org
In message <96Oct31.105634pdt."415911"@mule.parc.xerox.com>, Larry Masinter wri tes: ># road (b), but I want to argue that choice (a) is the choice you should >Yaron responded: >> I say we take the weasel way out and support both. The draft already allows >for this. > >But actually, I meant to make a stronger case that you should NOT try >to support choice (b): that is, don't try to allow for 'versioning' to >apply to resources that don't have URLs. Let me make an even stronger case, based not on anectodal evicence, encouragement or rhetoric, but plain logic: A representation (or entity -- same thing) is immutable, the way integers and URLs are immutable. How many versions of the number 2 or the string "http://www.w3.org/" are there? A representation is a sequence of bytes (the body) and a set of name/value string pairs in the header; all together, a sequence of bytes. Look at it as a big base-256 integer. It's still an integer, just like 2. No state. No changes. No versions. A resource, on the other hand, has state, attributes, related resources (i.e. linked resources, or variants, or versions, ...) etc. It's not directly observable: the only thing the world can know for sure about a resource is (1) it's URL, and (2) how it responds to requests like GET, and from that (3) which other resources are linked to/from it. From the outside, files, database entries, program computation results, etc. are indistinguishable. It makes perfect sense for an origin server to say (or for anybody to claim, for that matter) that: http://www.w3.org/file1;version-1.2 is the URL for a resource that represents version 1.2 of the resource at: http://www.w3.org/file1 But it makes no sense to say that the representation: Content-Type: text/plan abc is version 1.2 of the representation: Content-Type: text/plan def any more than it makes sense to say that the number 4 is version 1.2 of the number 2. Dan
Received on Thursday, 31 October 1996 14:26:44 UTC