Date: Wed, 7 May 1997 10:48:48 +0200 (MET DST) From: "Martin J. Duerst" <firstname.lastname@example.org> To: "Alain LaBont/e'/" <email@example.com> cc: URI mailing list <firstname.lastname@example.org> Subject: Re: "Difficult Characters" draft In-Reply-To: <email@example.com> Message-ID: <Pine.SUN.3.96.970507103030.245X-100000@enoshima> On Mon, 21 Apr 1997, Alain LaBont/e'/ wrote: > >Actually, you can write > > > >> http://wWw.lAmUtUeLlE.CoM/agent/home.htm?aid=S200569 > > > >and it will still work. But please leave the part after the first > >single slash alone. > > All right... That is not very user friendly. Totally inconsistent... from a > user perspective, undesirable... Yes, it's definitely not very consistent. But one has to be aware of the fact that URLs are patched together from an enormous variety of things, they are kind of a microcosmos reflecting a large number of internet and other software mechanisms. And all of these have different histories, different requirements, and so on, and this shows up in URLs. To take up the above examlpe, because DNS ignores case differences, it is impossible for URLs to decree that wWw.lAmUtUeLlE.CoM should not match with www.lamutuelle.com. On the other hand, because case differences in forms and query parts can be extremely relevant, it is impossible to decree, on the URL side, that aid=S200569 and aid=s200569 are equivalent, even though they might be made equivalent on the server side. So for URLs, and likewise for other kinds of identifiers, a general case equivalence policy is not possible. The only consistent and reliable message to users is: When transcribing URLs, take care of case (and all other details)! If you respect this message, you will never see bad surprises. The fact that in some cases some mistakes are tolerated has to be taken as a gift and is in no way guaranteed. And users that are not thought this message will find out quickly. > >In case there is indeed equivalence, as we currently have it in domain > >names, it will be the task of domain name internationalization to > >decide what to do about it, whether to make the usual domain names > >case sensitive or whether to introduce case eqivalences for characters > >outside ASCII or whatever. There is no problem with any kind of > >URL scheme or mechanism to introduce additional eqivalences where > >they see fit, but we can't introduce them for all URLs. > > I'm puzzled that the notion of consistency is neglected... I learned > something. Alain - The Internet is a highly dynamic, if not to say chaotic, environment. People always try to be consistent, but they also have their own ideas about how things should work. And the reason that DNS does case-equivalence is maybe in part due to some idea of user-friendliness, but mainly due to the fact that in the old times, there were quite a few computers that had difficulties representing both upper case and lower case. Regards, Martin.