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Re: What if an URI also is a URL

From: Richard Cyganiak <richard@cyganiak.de>
Date: Thu, 13 Sep 2007 18:54:44 +0200
Message-Id: <C01E2544-F50D-41EF-B77A-97F8E28C8A89@cyganiak.de>
Cc: Edward Bryant <edward.bryant@gmail.com>, semantic-web@w3.org
To: Reto Bachmann-Gmür <rbg@talis.com>

Reto,

On 13 Sep 2007, at 10:32, Reto Bachmann-Gmür wrote:
>> To learn what a URI refers to, don't look under the hood of the
>> server. Look at the representations returned via HTTP.
> While I'm not saying you should look under the hood of the server (or
> guessing from the URI)  looking at the representation returned by HTTP
> may not be enough, e.g.
> <http://Example.org/weather/ch/Bern/archive/2007-09-13> is probably  
> not
> identifying the same resource as <http://Example.org/weather/ch/Bern>
> even if (today) you would get the same representation.

Well, I'd say that the content provider acts against his own  
interests if he publishes the same representation at both these URIs.

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 Thursday, 13 September 2007 16:55:13 UTC

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