W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > January 2002

TDL is compatible with tidy literals, even if current TDL MT is not (which should be fixed)

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Mon, 28 Jan 2002 11:06:51 +0200
To: Jeremy Carroll <jjc@hplb.hpl.hp.com>, Dan Connolly <connolly@w3.org>
CC: RDF Core <w3c-rdfcore-wg@w3.org>
Message-ID: <B87AE14D.C6B6%patrick.stickler@nokia.com>
On 2002-01-25 19:22, "ext Jeremy Carroll" <jjc@hplb.hpl.hp.com> wrote:

> 
> 
> 
>> 
>> 
>> Brace yourself for mind-bogglinly deep
>> formal argument:
>> 
>> premise:
>> <http://www.w3.org/> dc:title "W3C".
>> conclusion:
>> <http://www.w3.org/> dc:title "W3C".
>> 
> 
> 
> I am reviewing this.
> Currently I think Dan has a point.
> 
> So ...
> 
> So as is, this is a show-stopping bug on TDL.

Forgive me for slightly disagreeing with you Jeremy, but
the bug is not with TDL, but with the present MT definition
of TDL.

The basis of TDL is that one interpretes a given literal
as a lexical form of a datatype based on which TDL pairings
are defined or inferrable from the RDF graph.

In essence, TDL interpretation is like an axiom:

Per local idiom:

IF   a literal L is the object of the predicate rdf:value
     and the subject is an ononymous node with an rdf:type
     property defined,
THEN the datatype D is the object
     of that rdf:type property and the TDL is (L, D)

Per global idiom:

IF   a literal L is the object of a predicate other than
     rdf:value
THEN for each datatype D associated with the predicate
     via an rdfs:range property, there is a TDL (L, D)

and once we have a TDL, we know the value, based on
the definitions in the foundational DT MT and the
1:1 relation between TDL pairings and mappings.

Note that in the above axioms, L is the actual literal
string, not the node, and D is the URI of the datatype
not the node/resource.

Neither of the above "axioms" require the graph to be
untidy for literals. The only thing that requires the
graph to be untidy is IFF the object node of a predicate
which either has a literal label or is an anonymous
node with an rdf:value defined literal is itself supposed
to denote the member of the value space. If the object
node need not denote the actual member of the value space,
then there's no problem.

See the attached illustration, which shows a literal tidy
graph where the literal "30" is interpreted as a lexical
form for two different datatypes. This shows that (a) the
TDL model itself is agnostic with regards to tidy versus
untidy literals, and also that the same literal (not
lexical form) may have multiple interpretations, depending
on the datatype associated with it.

Thus, I see no reason why the TDL MT cannot be revised
to allow tidy literals -- so long as folks are OK with
the axomatic like interpretation of TDL pairings and we
don't have to denote an actual value by any given literal
labeled node or rdf:value=literal qualified anonymous node.

> However it doesn't surprise me that there is a bug, very few of us produce
> bug-free stuff first time.
> The normal response to bugs (even showstoppers) is to fix them, so that's
> what I intend to do.

I have every confidence that the bug in the MT for TDL can
be fixed ;-)

Cheers,

Patrick


--
               
Patrick Stickler              Phone: +358 50 483 9453
Senior Research Scientist     Fax:   +358 7180 35409
Nokia Research Center         Email: patrick.stickler@nokia.com





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Received on Monday, 28 January 2002 04:05:51 EST

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