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Re: RDF-ISSUE-79 (undefined-datatype): What is the value of a literal whose datatype IRI is not a datatype? [RDF Concepts]

From: Pat Hayes <phayes@ihmc.us>
Date: Fri, 18 Nov 2011 10:35:05 -0600
Cc: RDF Working Group WG <public-rdf-wg@w3.org>
Message-Id: <8830765C-307B-4C40-9CAB-E0875A0B4BD5@ihmc.us>
To: Dan Brickley <danbri@danbri.org>

On Nov 9, 2011, at 3:11 PM, Dan Brickley wrote:

> On 9 November 2011 21:53, RDF Working Group Issue Tracker
> <sysbot+tracker@w3.org> wrote:
>> RDF-ISSUE-79 (undefined-datatype): What is the value of a literal whose datatype IRI is not a datatype? [RDF Concepts]
>> 
>> http://www.w3.org/2011/rdf-wg/track/issues/79
>> 
>> Raised by: Richard Cyganiak
>> On product: RDF Concepts
>> 
>> The RDF Concepts spec (in both 2004 and 1.1 versions) does not answer the question what's the value of a literal where the datatype IRI doesn't actually denote a datatype, like <"foo",http://example.com/not-a-datatype>. This is surprising, as there is a section that normatively defines the value of *all other* literals.
>> 
>> There are many possibilities:
>> 
>> (i) the spec leaves it undefined
>> (ii) that's not a valid RDF graph
>> (iii) it's a valid RDF graph, but the value, if any, is unknown
>> (iv) it's a valid RDF graph, and the literal is ill-typed
>> 
>> This should be made explicit.
>> 
>> The status quo is (i). I believe that the model theory says it's (iii).
> 
> -1 on (ii)
> I don't like the notion that a single illformed triple could in some
> sense "invalidate" a graph. There's a weaker sense in which the whole
> graph, considered as a description, is no longer going to be a true
> description in any interestingly relevant world. But "invalid" sounds
> harsher than that.

Um.. in the semantics document, "invalid" means exactly that, ie false in all interpretations. What it sounds harsher than is surely irrelevant. 

> 
> Note that even mentioning such a construct with RDF'99's reification
> vocabulary would (if (ii) were our rule) make the graph invalid. Which
> probably just goes to show that reification still isn't quoting.
> 
> I'm ok with (i) (iii) or (iv). Whatever we do or say we'll have lots
> of crap data and it'll get often get scrubbed somehow rather than
> rejected absolutely. XML-style 'catch fire and burn' strictness
> probably wouldn't serve us well here.
> 
> BTW how do we know a URI isn't a datatype?

Any URI might be the name of a datatype. The entailment regime you are working under when you make inferences is what decides whether it is being treated as one or not. 

Pat


> What about punning? e.g. it
> might be a datatype proposal...
> 
> Dan
> 
> 

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Received on Friday, 18 November 2011 16:35:41 GMT

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