- From: Larry Masinter <masinter@parc.xerox.com>
- Date: Fri, 13 Jun 1997 11:02:39 PDT
- To: HTTP Working Group <http-wg@cuckoo.hpl.hp.com>
This proposal isn't so different from things like wanting to 'vary' on just part of the User Agent string (this is Netscape specific, but I don't care about whether it's Netscape for Windows or for Unix) or, say, whether "image/png" appears in the Accept headers, but ignoring any other difference in Accept. The problem is that the granularity of 'Vary' is to name the header, but sometimes the variation only depends on a little bit of information in a single header and not the whole thing. I don't think we can invent a general solution to the problem in HTTP/1.1, because of the varying [sic] nature of the syntax of the various [sic] headers. User-Agent is parsed one way, Cookie is parsed another, and Accept is parsed yet another. The consolation is that even though you have to pay a round-trip for it, you won't have to send the content again, because the cache can send the entity tags of the variants it has, and have those validated; since you need the round trip anyway to update the rest of the state, perhaps there isn't a performance impact after all. Larry -- http://www.parc.xerox.com/masinter
Received on Friday, 13 June 1997 11:10:42 UTC