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RE: RDF speficiations (was RE: Cutting the Patrician datatype kno t)

From: <Patrick.Stickler@nokia.com>
Date: Sat, 8 Dec 2001 00:51:30 +0200
Message-ID: <A03E60B17132A84F9B4BB5EEDE57957B160B1B@trebe006.NOE.Nokia.com>
To: pfps@research.bell-labs.com
Cc: www-rdf-interest@w3.org
> For example, for XML Schema, the interface could pass a pair like
> <integer,10> or even <integer,"10"> instead of <decimal with 0
> fractionDigits union string,"010">.  This would be much easier for
> applications to handle than requiring them to understand all 
> of XML Schema
> constructed datatypes.

I believe this is very similar to what I am presently arguing, that data 
typing insofar as RDF is concerned is simply capturing the pairing of
lexical
form and data type identifier, and that there may be various ways to
do that, such as globally via rdfs:range or locally via an anonymous
node with rdf:value and rdf:type values. E.g.

both the global idiom (P)

   x ex:age "10" .
   ex:age rdfs:range xsd:integer .

and the local idiom (DAML)

   x ex:age _:1 .
   _:1 rdf:value "10" .
   _:1 rdf:type xsd:integer .

are two synonymous idioms which define the same pairing

  (xsd:integer,"10")

which, per the XML Schema spec, denotes the integer value 'ten'.

An application, when it needs to "deal with" a given value, should
simply be able to obtain the pairing (if it is defined) and execute
the mapping to the actual value in terms of that pairing.

A particular API could provide such mapping transparently, including
support for several idioms, global and local.

And by sticking to just this pairing of lexical form an data type,
we are able to support arbitrary data types in RDF, leaving the
interpretation/mapping to applications which support/understand
the particular data types in question.

Is this what you are also suggesting?

If so, then it would seem that the only real question requiring
resolution is which idioms should be used to define those pairings.
We'd need at least one each for global and local typing, and the
two current idioms in use (rdfs:range and DAML, as shown above) 
seem to do the job. There are others that may be useful in particular
contexts (e.g. U) and folks would be free to use them but they wouldn't
be the "standard" idioms that conformant tools would need to support.

So, to recap:

Do we really need anything more than the definition of the
pairing and at least two idioms for global and local definition
of such pairings? I say no.

Do we really want the MT itself to say whether the pairings 
(xsd:integer,"10") and (xsd:integer,"010") actually denote the 
same value or not? I think not.

Or do we rather leave such questions up to applications that 
"know about" the specific data types and is able to determine
such things? Yes, definitely.

We still need to work through some issues of class relations
and the semantics of e.g. rdfs:subClassOf and rdfs:subPropertyOf
with regards to data types (lexical vs. value spaces) but those
are issues that will have to be addressed no matter what idiom
is used to define pairings.

Cheers,

Patrick

--
               
Patrick Stickler              Phone: +358 50 483 9453
Senior Research Scientist     Fax:   +358 7180 35409
Nokia Research Center         Email: patrick.stickler@nokia.com
Received on Friday, 7 December 2001 17:51:40 GMT

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