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Re: Ill-typed vs. inconsistent?

From: Antoine Zimmermann <antoine.zimmermann@emse.fr>
Date: Fri, 16 Nov 2012 13:25:21 +0100
Message-ID: <50A630B1.9050104@emse.fr>
To: Richard Cyganiak <richard@cyganiak.de>
CC: public-rdf-wg@w3.org
Le 15/11/2012 20:33, Richard Cyganiak a écrit :
> On 14 Nov 2012, at 14:48, Antoine Zimmermann wrote:
>> The more I think of this issue, the more I believe that ill-typed
>> literals should be a syntax error. An application that supports a
>> datatype should reject RDF graphs that do not write literals of
>> that type properly.
>
> This would invalidate tons of existing RDF, so I don't think it's in
> the spirit of our charter:
>
> [[ For all new features, backwards compatibility with the current
> version of RDF is of great importance. This means that all efforts
> should be made so that any valid RDF graphs (in terms of the RDF 2004
> version) should remain valid in terms of a new version of RDF; ]]

Yes, you're right.

>
>> Note that in OWL 2 Structural Specification and Functional Style
>> Syntax, it is required that:
>>
>> "The lexical form of each literal occurring in an OWL 2 DL ontology
>> MUST belong to the lexical space of the literal's datatype."
>
> But that's just for OWL DL, right? Which isn't a proper extension of
> RDF Semantics anyway, right? How are ill-typed  literals treated in
> the rest of OWL?

Yes, it's for OWL DL of course since the syntax of OWL Full is exactly 
RDF. But the notion of "semantic extension" in RDF Semantics 2004 allows 
for syntactic restrictions.

"""
The semantic conditions imposed on an RDF semantic extension MUST define 
a notion of vocabulary entailment which is valid according to the 
model-theoretic semantics described in the normative parts of this 
document; except that if the semantic extension is defined on some 
syntactically restricted subset of RDF graphs, then the semantic 
conditions need only apply to this subset.
"""

and:

"""
General monotonicity lemma. Suppose that S, S' are sets of RDF graphs 
with every member of S a subset of some member of S'. Suppose that Y 
indicates a semantic extension of  X, S X-entails E, and S and E satisfy 
any syntactic restrictions of Y. Then S' Y-entails E.
"""


Anyway, I'm afraid we are going to have no changes wrt the situation of 
ill-typed literals.


AZ


>
> Best, Richard
>


-- 
Antoine Zimmermann
ISCOD / LSTI - Institut Henri Fayol
École Nationale Supérieure des Mines de Saint-Étienne
158 cours Fauriel
42023 Saint-Étienne Cedex 2
France
Tél:+33(0)4 77 42 66 03
Fax:+33(0)4 77 42 66 66
http://zimmer.aprilfoolsreview.com/
Received on Friday, 16 November 2012 12:26:31 GMT

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