- From: <jalgermissen@topicmapping.com>
- Date: Mon, 22 Sep 2003 16:50:02 +0200
- To: Tim Bray <tbray@textuality.com>
- Cc: Norman Walsh <Norman.Walsh@Sun.COM>, <www-tag@w3.org>
Tim Bray <tbray@textuality.com> schrieb am 22.09.2003, 16:27:22: > > Norman Walsh wrote: > > > In section 2.2, URI Opacity, we say: > > > > Although it is tempting to guess at the nature of a resource by > > inspection of a URI that identifies it, this is not licensed by > > specifications; this is called URI opacity. > > > > Then later on we say > > > > mailto URIs identify mailboxes; ftp URIs identify ftp files and > > directories; etc. > > > > It seems to me that these two statements are in conflict. Either you > > aren't allowed to guess the nature of a resource from its URI, or you > > are: it can't be both ways. > > Not in the slightest. It is perfectly OK for software to look at the > URI scheme and act on that basis, the semantics of URI schemes are > well-documented. The problem is looking into the opaque part, i.e. > assuming that http://www.tbray.org/ongoing/Biz is a directory, or that > http://example.com/foo.html yields HTML when dereferenced. Does the > spec need to be clearer on what's OK and what's not? -Tim Tim, as a pure consumer of the spec I'd say, yes, it is not clear. Here is what I *think* about URI opacity and URI schemes: - the semantics of the resource (what the nature of the resource is) may not be inferred from the URI - the way to interact with the resource may be inferred from the scheme. So, given a ftp:// URI software can invoke FTP operations on the resource but may not infer that the resource's nature is 'FTP file' (whatever that means). So, if I am right, then "mailto URIs identify mailboxes; ftp URIs identify ftp files and directories; etc." is misleading because one may understand from this that there is a semantic (as opposed to purely technical/software oriented) class of resources that is called 'mailbox' and that all ftp:// URIs are instances of 'mailbox'. Or is my understanding of the issue wrong? Jan -- Jan Algermissen <algermissen@acm.org> Consultant & Programmer http://www.topicmapping.com http://www.gooseworks.org
Received on Monday, 22 September 2003 10:52:12 UTC