- From: Sean B. Palmer <sean@mysterylights.com>
- Date: Fri, 18 May 2001 15:58:23 +0100
- To: "Pierre-Antoine CHAMPIN" <champin@bat710.univ-lyon1.fr>, "Aaron Swartz" <aswartz@swartzfam.com>
- Cc: "RDF Interest" <www-rdf-interest@w3.org>
> Some document in DI claims that there is no fundamental > difference btw URIs and URI refs. [...] Hmm... maybe you're reading a totally different set of TimBL's DesignIssues to me. How could there be no fundamental difference between URIs and URI refs? The complication (annoyance) is that in RDF, a "resource" can be identified by a URI or a URI-Ref, whereas in the URI RFC, a resource is what's identified by a URI, and a URI-Ref is a "view" of that resource. It was a bit foolish to reuse the same word for a different concept. Still, according to TimBL (as far as I can tell from DesignIssues) in HTTP, a URI identifies some material "suitable for HyperText transfer", but not some kind of generic concept. Some people disagree with this (Sandro?), stating that "the homepage of Dan" can also be used to represent Dan himself, as long as the two aren't muddled... but it's murky ground. Anyway, I think that the following is quite explicit:- [[[ It is important, on the Semantic Web, to be clear about what is identified. An http: URI (without fragment identifier) necessarily identifies a generic document. This is because the HTTP server response about a URI can deleiver a rendition of (or location of, or apologies for) a document which is identified by the URI requested. A client which understands the http: protocol can immediately conclude that the fragementid-less URI is a generic document. This is true even if the publisher (owner of the DNS name) has decided not to run a server. Even if it just records the fact that the document is not available online, still a client knows it refers to a document. This means that identifiers for arbitrary RDF concepts should have fragment identifiers. This in term means that RDF namespaces should end with "#". ]]] - http://www.w3.org/DesignIssues/Fragment Because "resources" in RDF covers URI-Refs as well, I normally use namespaces with a "#" on the end just to be safe. It's easier for maintainance purposes that way as well (although not always). -- Kindest Regards, Sean B. Palmer @prefix : <http://webns.net/roughterms/> . :Sean :hasHomepage <http://purl.org/net/sbp/> .
Received on Friday, 18 May 2001 11:47:54 UTC