dcat:accessURL issue

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.











[1] https://dvcs.w3.org/hg/gld/raw-file/default/dcat/index.html

[2] http://www.w3.org/ns/dcat.ttl



Makx Dekkers

 <mailto:makx@makxdekkers.com> makx@makxdekkers.com

+34 639 26 11 46



Received on Thursday, 31 January 2013 13:58:16 UTC