W3C home > Mailing lists > Public > public-swd-wg@w3.org > January 2009

Re: Values and rdf:value

From: Antoine Isaac <aisaac@few.vu.nl>
Date: Thu, 08 Jan 2009 19:19:28 +0100
Message-ID: <496643B0.3060009@few.vu.nl>
To: Thomas Baker <baker@sub.uni-goettingen.de>
CC: Ivan Herman <ivan@w3.org>, SWD Working Group <public-swd-wg@w3.org>



> I always thought the motivation for rdf:value was to allow for
> a sort of "dumbing down".  Book A has an author (dc:creator)
> with the name "John Brown", birthdate "1942", and shoe size
> "12E".  rdf:value, then, designates a handle of sorts for
> the resource as a whole - in this case, most obviously, its
> name ("John Brown").  I had always assumed that the object
> of rdf:value was intended to be a literal (as in the SKOS
> Primer example in Section 4.2) though I see that its formal
> range is rdfs:Resource.
> 
> Given my interpretation, then, I would restate the sentence
> from RDF Semantics (below) to mean:
> 
>     It is typically used to identify a 'primary' or 'main'
>     value of a property which has several values -- that is,
>     of a property which has as its value a complex entity
>     with several facets or properties of its own.
> 
> which seems to be the opposite of your reading:
> 
>> I guess what they mean is that the object of rdf:value is a 'general
>> non-literal resource' that I used in my previous mail.
> 
> But the rdf:value thing is just part of the broader issue,
> which is whether it is formally proper (and pedagogically
> desirable) to refer to objects of triples as "values".  Do we
> think the 2004 specs are out of synch with current usage in
> this regard?
> 
> The other question is whether we feel confident that the
> use of rdf:value in the example in Section 4.2 represents
> "typical" usage ("This is typically done using the RDF
> rdf:value utility property").


Sorry, it was difficult to resist coining an example as my two cents:

ex:sun ex:volume ex:sunDiameterKM .
ex:sunDiameterKM rdf:value "1392000000" ;
   ex:unit "m"

In that case, we have a diameter (expected to be called in language a "value") which is complex: it has two facets, the raw "value" (confusing, but how to name it differently?) and the unit.

Now, I can imagine that someone may actually want to decompose the value itself to fit another standard way of representing it, but keeping the same value-unit pattern:

ex:sun ex:volume ex:sunDiameterKM2 .
ex:sunDiameterKM2 rdf:value [ ex:coefficient "1.392" ; ex:exponent "9" . ] ;
   ex:unit "m"

The latter example has an rdf:value which is a non-literal RDF node...
Granted, it's not a nice example, and there might be ways now to do it in a much nicer way. But I guess at the beginning of RDF some people may have judged useful to anticipate that kind of practice.

> 
> For the sentence in question, Alistair points out that we
> can side-step the issue by just defining RDF plain literal,
> full stop [1].  
> 
> If the RDF Primer is telling a somewhat different story
> from SKOS Primer it would be good to recognize this clearly
> because readers of the latter may refer back to the former.

Until now I don't think the documents are really saying really different things. In fact the Primer does not use rdf:value and "value" not very often...

Actually it is used now once in a possibly confusing way, in 4.6
> The value of the literal is the notation itself
I propose to replace it by "The lexical form of the literal is the notation itself"

Antoine

> 
> [1] http://lists.w3.org/Archives/Public/public-swd-wg/2009Jan/0026.html
> 
Received on Thursday, 8 January 2009 18:20:07 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Thursday, 8 January 2009 18:20:07 GMT