Re: Question about namespace

André, Tatiana, 

please see TimBL's view [1] on the distinction of URNs and URLs, please
note that the Web Architecture [2] doesn't distinguish between such
categories and please see section 1.1.3 or the definition of URI (RFC
3986 [3]) that suggests that the distinction is not so clear and that
the generic term URI should be used instead.

In short, the distinction between URNs and URLs is not clear,
furthermore it's useful for URNs to be resolvable (to be URLs) and it's
also useful for URLs to be persistent (to be URNs). Both are useful for
usability of the Web and for fulfilling of the normal person's
expectations: that bookmarks will work for some considerable time and
that any URI, when put in the address bar of a browser, will give me
something useful.

Also, the point below that URNs are not restricted to a physical
location is somewhat dubious, as purl.org certainly does have a physical
location. What purl.org provides is indirection, a known way to increase
persistence, but one doesn't need purl.org for that.

Finally, there is a urn: URI scheme and URIs in this scheme don't
necessarily contain any physical host information, which may make them
more persistent but it makes them a lot less useful when someone sees
such a URI for the first time.

Please consider using the term URI and making your http: URIs
persistent. 8-)

Hope it helps,

Jacek Kopecky



[1] http://www.w3.org/DesignIssues/NameMyth.html
[2] http://www.w3.org/TR/webarch/
[3] http://mirror.switch.ch/rfc/3986.txt

On Fri, 2005-08-26 at 16:31 -0300, Andre Santanche wrote:
> Tatiana Vieira escreveu:
> > Hi people,
> >  
> > As the topic here is namespace, let me ask a question. If a namespace 
> > isn't necessarily an URL (it isn't necessary to be a physical location), 
> > how can anyone discover the concepts declared in an ontology? I mean, 
> > how can I use a specicified vocabulary defined in any place in Web if 
> > I can't find it?
> >  
> > And, also, how can we be sure that namespaces will not conflict, I mean, 
> > that two diferent users will not put an igual namespace for different 
> > documents?
> 
> URIs are divided in two categories: URLs and URNs. The URL adoption can 
> be controlled by the URL owner, for example, my lab has an URL: 
> http://www.lis.ic.unicamp.br, and any sub-URL is agreed by the lab 
> members. Additionally, I have a personal URL inside the lab 
> http://www.lis.ic.unicamp.br/~santanch, then I can decide the sub-URLs.
> 
> However, I prefer the use of URNs that are not restricted to a physical 
> location, and can be directed to any URL you want. There are many URN 
> services. You could, for example, take your own URN for free in 
> http://www.purl.org/. The server guarantees that nobody will take the 
> same URN given to you.
> 
> > Thank you in advance,
> > Tatiana.
> 
> Regards,
> 
> André Santanchè
> 
> 
>

Received on Tuesday, 30 August 2005 18:46:26 UTC