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Re: dcat:accessURL issue

From: Fadi Maali <fadi.maali@deri.org>
Date: Thu, 31 Jan 2013 14:39:49 +0000
Cc: "'Richard Cyganiak'" <richard@cyganiak.de>, "Public GLD WG" <public-gld-wg@w3.org>
Message-Id: <DA2C56FC-B65C-4EB1-B00D-958CE3322480@deri.org>
To: "Makx Dekkers" <mail@makxdekkers.com>
Hi Makx,

Thanks for your email. 
The difference between the Turtle and the HTML is a mistake! my bad!
However, I think the correct value is rdfs:Resource. 
I think it is the correct way to do it and also seems to be more common in RDF. For example, foaf:page is defined with Document as a range

This thread on answers.semanticweb.com provides some opinions and clarifications:
http://answers.semanticweb.com/questions/2882/why-are-uris-sometimes-treated-as-literals-in-rdf

The consensus there seem to be with using the URI to talk about the thing identified by the URI and use a literal when talking about the string of characters constituting the URI
similar to the examples you provided...

On 31 Jan 2013, at 13:57, Makx Dekkers wrote:

> Dear Fadi, Richard,
>  
> In preparation for the DCAT call this afternoon, I wanted to raise an issue concerning the property dcat:accessURL.
>  
> First of all, it was pointed out to me that there is a difference in definition between the latest editor’s draft [1] (no header, no date) and the Turtle spec [2]. In [1] the range is rdfs:Literal and in [2] it is rdfs:Resource.
>  
> Now, if I am allowed to express my opinion here, I think an accessURL can only be a rdfs:Literal and not a rdfs:Resource, even if it looks like a URI.
>  
> The main problem that I see is that an accessURL is a string of characters that happen to be a URL. However, the URL is not the thing it points to. In a way, on the theoretical level, saying that the URL is the resource would be equivalent to saying that the range of a name is a resource if it happens to look like a URL.
>  
> But on a practical level, while I can say:
>  
> “The foaf:name ‘Makx Dekkers’ contains 12 characters”,
>  
> if I were to say
>  
> “the dcat:accessURL ‘http://t.co/xyz’ contains 15 characters”
>  
> it would mean that this *string* has 15 characters if it is declared as an rdfs:Literal, but it would mean that the *document* at that URL is  15 characters long.
>  
> Even worse, if it is defined as a resource,  I would not be able to make a statement like:
>  
> “the dcat:accessURL ‘http://t.co/xyz’ is a valid URI” (unless of course the *document*contains text that is a valid URI).
>  
> The second problem is that the definition of accessURL as resource seems to use URL and URI interchangeably. While I agree that it is true that every URL is a valid URI (by definition), the converse is not true. I read in RFC 3986:
>  
> The term "Uniform Resource Locator" (URL) refers to the subset of URIs that, in addition to identifying a resource, provide a means of locating the resource by describing its primary access mechanism (e.g., its network "location").
>  
> In this sense, I think the value of dcat:accessURL is not always a URI as the issue listed just above the definition of accessURL in https://dvcs.w3.org/hg/gld/raw-file/default/dcat/index.html states.

The value of accessURL is always a URL which is a URI.

We can discuss more during the telco… I'm sure accessURL will take most of today's discussion!

Regards,
Fadi

>  
> Makx.
>  
>  
>  
>  
>  
>  
>  
>  
> [1] https://dvcs.w3.org/hg/gld/raw-file/default/dcat/index.html
> [2] http://www.w3.org/ns/dcat.ttl
>  
>  
> Makx Dekkers
> makx@makxdekkers.com
> +34 639 26 11 46
>  
Received on Thursday, 31 January 2013 14:40:23 UTC

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