RE: Literals (Re: model theory for RDF/S)

> -----Original Message-----
> From: ext Ora Lassila [mailto:daml@lassila.org]
> Sent: 08 October, 2001 12:02
> To: Stickler Patrick (NRC/Tampere)
> Cc: www-rdf-logic@w3.org
> Subject: Re: Literals (Re: model theory for RDF/S)
> 
> 
> Patrick,
> 
> let's get vocabulary straight:
> 
> Patrick.Stickler@nokia.com wrote:
> 
> 
> > Those who prefer weak data typing can just use untyped (or at
> > best implicitely typed) literal strings, and those who prefer
> > strong data typing can use e.g. URI encoded typed data values.
> 
> 
> Just to clarify, when I spoke about weak vs. strong typing, I 
> meant in 
> the traditional programming language sense. That is, weak 
> means that the 
> type information is carried in the data, and strong means that the 
> information is carried by the program. Untyped is sort of off 
> the chart 
> in this respect.
> 
> In RDF, the schema is the equivalent of a "program", so what 
> you refer 
> to as strong is actually weak. Strong typing in RDF would 
> require access 
> to the schema where the type information is contained.
> 
> 	- Ora


You're right. I got it backwards. Thanks alot for pointing that out.

If I understand you, a specific RDF Schema (or collection of
collaborative schemas) is the "program" which defines the strong data 
typing -- but (presumably) if and only if for every property that
can take a literal value there is defined one and only one range
and that range defines the type of the property and all values
the property can take. Once you allow multiple ranges, or fail
to define a range for a property, you lose your strong data typing,
right?

And, insofar as the standardized mechanisms are concerned, RDF literals
in their minimal representation (as the immediate values of a property)
and in the absence of any RDF schema defining ranges of properties,
are "untyped" (or at best, corresponding to the type 'sequence of Unicode
values'), as they neither carry their type information with them, either
by qualified anonymous node or schema defined range.

To that end, RDF in essence allows strongly typed, weakly typed, and
untyped property/value pairs all in the same knowledge base, depending
on the mechanisms used for the particular property/value pairs in
question.

Thus, it's a matter of perspective and level/scope as to whether one can
call a given RDF application strongly or weakly typed. Eh?

Cheers,

Patrick

--
Patrick Stickler                      Phone:  +358 3 356 0209
Senior Research Scientist             Mobile: +358 50 483 9453
Nokia Research Center                 Fax:    +358 7180 35409
Visiokatu 1, 33720 Tampere, Finland   Email:  patrick.stickler@nokia.com

Received on Monday, 8 October 2001 06:30:35 UTC