W3C home > Mailing lists > Public > semantic-web@w3.org > September 2007

Re: What if an URI also is a URL

From: Richard Cyganiak <richard@cyganiak.de>
Date: Fri, 14 Sep 2007 20:06:04 +0200
Message-Id: <A35E2A81-0C69-4B05-BC44-DBFCC770EC77@cyganiak.de>
Cc: semantic-web@w3.org, Reto Bachmann-Gmür <rbg@talis.com>, Edward Bryant <edward.bryant@gmail.com>
To: Oskar Welzl <lists@welzl.info>

On 14 Sep 2007, at 00:01, Oskar Welzl wrote:
> The main trouble with URIs is not finding out what they identify when
> you stumble across them in some RDF... thats trivial, even machines  
> can
> do it.

Well, it might seem trivial, but the question still manages to  
generate a *lot* of discussion ... ;-)

> The trouble is finding the right ones for RDF you write yourself.
> "Right" in this context means there's a chance of other's using the  
> same
> URI for the same thing, which *should* be easier for things 'on the  
> web'
> than in general. Or so I thought before...

Hm, I don't see the trouble.

Want to find a URI for something?

If you know that it is an existing web resource, use its URI.

Otherwise, mint a new URI.


You should never be afraid of minting new URIs, even if there might  
be an existing one out there already. If you learn about a good  
existing URI later, then you can still declare it owl:sameAs. Not  
knowing a good existing URI for something should never stop you from  
publishing RDF data about that thing.

That being said, there are lots of great resources for finding  
existing SemWeb-friendly URIs. You can use the SemWeb search engines,  
e.g. SWSE, Swoogle, Uriqr. Lots of good stuff can be found around the  
Linking Open Data project. If it exists in Wikipedia, then it has a  
URI in DBpedia. If none of these turn up anything useful, then mint  


> Oskar
>> It's a good practice to explain the nature of the resource somewhere
>> within the representation. So somewhere in the first one from your
>> example there might be the text
>> “This is the archived weather report of 13 September 2007 for the
>> city of Bern, Switzerland.”
>> while in the second one we might find
>> “This is the current weather report for the city of Bern,  
>> Switzerland.”
>> Or some equivalent RDF triples if we talk about Semantic Web content.
>> In the absence of such an explanation, an agent has little hope to
>> find out what he's looking at. He cannot use the URI to reliably
>> refer to anything, because he doesn't know what it will return
>> tomorrow. Bookmarking it, linking to it, or passing it on to someone
>> else, becomes a perilous affair. After all, I'd really like to know
>> if I'm looking at today's or yesterday's weather report. A weather
>> report that doesn't give me that information won't be popular.
>> Thus, both content consumer and content provider benefit from
>> representations that explain the nature of the resource.
>> A second, less helpful choice would be external information about the
>> resources. For example, there might be an RDF file or HTML file at
>> <http://Example.org/weather/> that tells us what all the individual
>> URIs refer to.
>> Richard
>>> Cheers,
>>> Reto
Received on Friday, 14 September 2007 18:06:37 UTC

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