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Re: What fourth column should be

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Wed, 16 Nov 2011 20:53:51 +0000
Message-ID: <4EC422DF.3060304@epimorphics.com>
To: public-rdf-wg@w3.org


On 16/11/11 17:59, Steve Harris wrote:
> On 2011-11-16, at 17:23, Antoine Zimmermann wrote:
>
>> As we ran out of time to discuss this, I would like to say that
>> having literals in the 4th position of N-Quads is very useful.
>> Especially, think about xsd:dateTime, xsd:anyURI.
>>
>> The advantage of this is that what typed literals denote is
>> unambiguous. So you know you are referring to the time when using
>> an xsd:dateTime-typed literal. You also know that you are referring
>> to a URI when using xsd:anyURI, instead of referring to the thing
>> denoted by the URI.
>>
>> It makes extensions of RDF easier for, e.g., temporal RDF, RDF with
>> trust (use a xsd:decimal to indicate level of trust/confidence),
>> provenance-RDF (use xsd:anyURI to denote the provenance URL
>> unambiguously), etc.
>>
>> If one uses a URI instead, it is always up to interpretations what
>> that URI denotes. It could denote the graph itself but could as
>> well denote the document where the triple is found or the main
>> entity in the graph, as we already discussed. Using a URI is more
>> flexible, though, so it must be allowed too.
>
> For the record I don't feel this is a good idea. There are many
> systems that implement quads, but I'm not aware of any that allow
> literals in the 0th/4th slot. that suggests that users haven't
> requested it much, and that we don't have implementation experience.
>
> I'm not sure how many systems that track time and/or provenance can
> be boiled down to a single literal  trust=0.23, or date=2011-11-16
> seems a bit simplistic  it certainly wouldn't work for us.

I agree.

One of the practical difficulties of reification is that working at the 
triple level is at odds with the fact that data comes in graphs. 
Reification provides building block but it becomes very verbose when you 
clump statings together, and the way you group them is non-standard.

With temporal or provenance usages, I think it is also the graph that is 
the useful unit.

	Andy
Received on Wednesday, 16 November 2011 20:54:21 GMT

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