- From: Lee Jonas <lee.jonas@cakehouse.co.uk>
- Date: Thu, 12 Apr 2001 15:23:34 +0100
- To: "'Charles McCathieNevile'" <charles@w3.org>, Lee Jonas <lee.jonas@cakehouse.co.uk>
- Cc: "'Aaron Swartz'" <aswartz@swartzfam.com>, RDF Interest <www-rdf-interest@w3.org>
Charles McCathieNevile [mailto:charles@w3.org] wrote: >Yes, I assert that it is risky to make statements about something when you >don't know how good your identifier is. (Although it is possible to state >that "I think this resource might disappear", or "statements made about this >resource at date XXXX are no longer valid, but do apply to resource YYYY" - >the latter is one of the things I am trying to work out how to do in EARL, >where we need to do it for different reasons) > >But I don't understand how a publisher of URNs guaranteeing that they remain >stable is any better than a publisher of URIs making the same guarantee. The >problem to be solved is a human one, not a technical one, as I see it. > Of course, on this you are entirely correct. Stable URNs are no better than stable URLs for identifying resources. But, from your earlier post, the URL mailto:veggiemite-beast@w3.org identifies the person at the W3C that eats the most veggiemite. The URL can remain stable, whilst being updated daily to reflect the person at the W3C who ate the most veggiemite that day. If you want to make RDF assertions on that basis then this URL is the most appropriate identifier. However, if one wants to make assertions about Charles Cavendish McCathieNevile, they shouldn't use mailto:charles@w3.org, because you may leave and another Charles may take over your mailbox - it would be inappropriate to use mailto:charles@w3.org unless you were making assertions about the owner of the charles mailbox at W3C. This can be generalised to all URLs where the publisher does not explicitly state that they will never change the resources represented. Instead of using an identifier to locate Charles Cavendish McCathieNevile as the owner of the "charles" mailbox at W3C, it would be better to assign you a globally unique identifier (e.g. a UUID) that will still identify you after you leave the W3C, and make assertions about you via that identifier. >From another perspective, the semantic web seems like a very good use case >that encourages publishers of URIs not to break them. Thereby making the idea >of introducing URNs less and less interesting... > The use of URNs is not to overcome stability of URLs but to overcome transience in the resources they represent. The semantic web might be more likely to make assertions about resources that are not intended to be electronically accessible, like Charles Cavendish McCathieNevile, meaning that the need for URNs increases, not diminishes. regards Lee >cheers > >Chaals > >On Thu, 12 Apr 2001, Lee Jonas wrote: > > >From what you say, use of URLs in RDF must be treated with extreme caution. > Unless a publisher guarantees that they won't change the fundamental nature > of the resource identified by a URL, you cannot rely on it to identify what > you intend it to. > > This seems like the most compelling argument for using URNs for identifying > anything other than representation mappings yet! > > regards > > Lee > > >-- >Charles McCathieNevile http://www.w3.org/People/Charles phone: +61 409 134 136 >W3C Web Accessibility Initiative http://www.w3.org/WAI fax: +1 617 258 5999 >Location: 21 Mitchell street FOOTSCRAY Vic 3011, Australia >(or W3C INRIA, Route des Lucioles, BP 93, 06902 Sophia Antipolis Cedex, France)
Received on Thursday, 12 April 2001 10:23:53 UTC