http://norman.walsh.name/2005/06/19/httpRange-14 8 94 2005-06-19T15:50:54-04:00 $Date: 2005-09-11 10:27:02 -0400 (Sun, 11 Sep 2005) $ Norman Walsh 2005 Norman Walsh A compromise has been reached, at least among those of us on the TAG. I hope the larger community will accept the compromise as well. T. E. Hulme Language is by its very nature a communal thing; that is, it expresses never the exact thing but a compromise—that which is common to you, me, and everybody. Records show that httpRange-14 was raised to the TAG on 25 March 2002. We've been debating its resolution for more than three years. I will not attempt to recapitulate that debate in any detail; your search engine of choice will no doubt lead you to it. Suffice it to say that some folks think http://example.org/some/path must identify “a document” (what the AWWW calls an “information resource”) and some folks think it can identify anything at all. These world views are not compatible. We've gone around and around and around searching for a compromise. And at last, we have found one. Remember: this is a compromise. What's needed here is something that everyone can live with, not something that necessarily makes everyone happy. Before you cry foul, if you're inclined to do so, consider carefully whether you think any better compromise is possible. Personally, I don't. So here it is. Given an http: URI without a fragment identifier, http://example.org/some/path, you can't tell if it's an information resource or something more general. That's ok, given http://example.org/some/path#fragid, you can't tell what that is either. Maybe that's a hole in the web architecture, maybe it isn't, but this compromise doesn't introduce that problem. The bottom line is, if you haven't gone off and retrieved it yourself, maybe you believe what someone tells you about the URI and maybe you don't. Let's say you want to check, so you go out and attempt to dereference the URI: If you get back 200 OK: The resource is an information resource. That means it isn't a car or a person or an idea. If you get back 303 See Other: The resource could be an information resource or it could be something more general. Maybe it is a car or a person or an idea, but maybe it's just a web page too. Hopefully the “see other” thing will help you figure that out. If you get back 404 Not Found: The nature of the resource is unclear. You haven't learned anything. You don't learn anything for any of the other 4xx errors either. This compromise allows vocabularies (like Dublin Core, FOAF, and Wordnet) to continue to use “slash” instead of “hash” for pragmatic reasons. It also preserves the common understanding that if you dereference a URI and you get back a document, that document is in some significant sense the thing you were attempting to get. At the same time, it allows you to use any URI you want for any resource you want, as long as you are willing to take some care in how you serve up representations for it.