- From: Stefano Mazzocchi <stefano@apache.org>
- Date: Sat, 20 Sep 2003 00:01:08 +0200
- To: Tim Berners-Lee <timbl@w3.org>
- Cc: www-tag@w3.org
On Sunday, Sep 14, 2003, at 19:59 Europe/Rome, Tim Berners-Lee wrote: > > On Saturday, Sep 13, 2003, at 15:56 US/Eastern, Stefano Mazzocchi > wrote: > >> >> From the current state of affairs, the web is based on URIs. From >> what I see, this is unlikely to change and I'm cool with this, >> expecially because URIs that are general enough to indicate anything, >> even concepts that are not "locatable". > > What do you mean by, "not locatable"? There are things, like abstract > concepts, > which may not be objects you find on the web, but they are things > which one describe. Sorry, I used the wrong terminology. I meant "dereferencable". >> Then, please, tell me: if these concepts are not locatable, why are >> we supposed to use the HTTP protocol to indicate them? >> >> I know, I know: in order to keep them unique using the domain name >> facilities... but ask yourself why in hell a namespace URI such as >> >> http://www.w3.org/1999/xslt >> > > The XSLT namespace is in fact > > http://www.w3.org/1999/XSL/Transform I stand corrected. Sorry. > An engineer who comes across a document which > uses that namespace can look it up, and get information > leading him or her to the XSTL specification. > > This is useful. So while a namespace seems like an abstract > concept, to actually refer to it by the name of something > which can be looked up is variable. [I assume you meant 'valuable'] > In the semantic web, information can be used not only be > a person, but by a machine. So while the concept > of "two-digit US state code" may be a an abstract property, > in fact one can find the list of them and the correlation with > various other properties. This is powerful. Very true. But the above triggers another question: what is the difference between an HTTP URI and an HTTP URL, if the first is supposed to be dereferencable as well? [I know this is a rather philosophical question, but anyway] >> is not >> >> uri://w3.org/xslt/1.0 >> >> where: >> >> 1) there is no misleading since the protocol clearly indicate its >> "unlocatable" status > > You presumably mean that no one should ever look up what the > owner of the name said about it. > You need the "urn:" prefix not "uri:". > But betware that many urn: subschemes are actually less useful > because they are waiting for some sort of lookup mechanism, > and to the extent they have such a mechanism, they become just clumsier > versions of http: Good point. >> 2) the domain-based uniqueness is maintained, no, improved, given >> that virtualhosts are not considered meaningful (there is no location >> taking place, just unique identification) > > The difference is an attitude of mind, and a mode of use. > Think of what you would like from your "uri:" space above, and use > http: > space like that. > > Use them like names not like locations. They are not locations. But you say that they are better than names because they might act as locations. Did I understand correctly? >> 3) version numbers are used instead of years. this makes them much >> easier to remember (you remember the version of the namespace you >> want to associate your content with, not the year that version was >> published [unless the year *is* the version, like in >> win95/98/2000/2003, but it's not the case here]) > > That is a question of web site management. > The advantage of years is that in 100 years time, when someone > wants to reuse they string "xslt", they will not have a problem. I see. Thanks for taking the time to answer. -- Stefano.
Received on Friday, 19 September 2003 18:02:18 UTC