RE: language tags in typed RDF literals

> -----Original Message-----
> From: ext pat hayes [mailto:phayes@ai.uwf.edu]
> Sent: 12 February, 2003 18:52
> To: Stickler Patrick (NMP/Tampere)
> Cc: w3c-rdfcore-wg@w3.org
> Subject: RE: language tags in typed RDF literals
> 
> 
> >A third option is that the lang tag is not significant to XMLLiteral,
> >or that XMLLiteral is not treated as a datatype, but as a third type
> >of literal, as it used to be, either of which would be my preferance.
> >
> >I.e. the problem is with XMLLiteral, and the correction should be
> >to XMLLiteral.
> 
> I'm sympathetic to that idea, but I think that is just a cosmetic 
> change to the wording. The semantics has to treat the built-in 
> datatype as a special syntactic case already. The real issue remains: 
> lang tags in typed literals are allowed by the syntax, but required 
> to be meaningless by the semantics, which seems dumb.  Either we 
> should get rid of them in the syntax, or we should let them be at 
> least potentially meaningful in the semantics.

If I had to choose (and only if I had to choose) I'd prefer
to remove the lang tags than make them significant to datatyping.

It means more work for us, and switching to other mechanisms for
language scoping/selection of assertions, but that would be the
lesser of the two evils, by a large margin.

Patrick


> Pat
> 
> >Patrick
> >
> >>  -----Original Message-----
> >>  From: ext pat hayes [mailto:phayes@ai.uwf.edu]
> >>  Sent: 12 February, 2003 02:01
> >>  To: www-rdf-comments@w3.org
> >>  Cc: bwm@hplb.hpl.hp.com; Jan.Grant@bristol.ac.uk
> >>  Subject: language tags in typed RDF literals
> >>
> >>
> >>
> >>  The current design of RDF literals is needlessly 
> complicated and kind
> >>  of silly.  The syntax allows language tags to occur in typed
> >>  literals, but in all cases other than rdf:XMLLiteral, 
> these tags are
> >>  required to have no meaning, so the semantics is obliged 
> to provide a
> >>  valid inference rule which allows any language tag in any 
> such typed
> >>  literal to be removed or replaced by any other.  This considerably
> >>  complicates the statement of the semantics, adds a burden to any
> >>  implementation, nullifies the implicit design principle 
> that literals
> >>  can be compared for identity using simple lexical 
> matching (since an
> >>  engine is required to strip out all such lang tags while 
> performing
> >>  inferences or checking for identity), and provides no useful
> >>  expressive function.
> >>
> >>  A related point is that the requirement in the semantics that
> >>  datatypes other than rdf:XMLLiteral *must* ignore 
> language tags seems
> >>  to restrict possible future datatyping proposals needlessly.
> >>
> >>  I suggest therefore that
> >>
> >>  EITHER
> >>
> >>  (1) lang tags be forbidden by the RDF syntax from appearing in
> >>  non-XML typed literals.
> >>
> >>  OR ELSE
> >>
> >>  (2) the notion of the lexical space of a datatype be 
> generalized to
> >>  allow (not require)  lang tags to be taken into consideration by a
> >>  datatype, so that the lexical space may be a set of 
> strings or pairs
> >>  of strings, i.e. a set of simple literals. This would 
> have the effect
> >>  that it would no longer be valid to make arbitrary 
> changes to a lang
> >>  tag in any literal, typed or not. It would also bring the 
> treatment
> >>  of all RDF datatypes into alignment so that 
> rdf:XMLLiteral need not
> >>  be considered a special case.
> >>
> >>  Either of these changes will simplify the semantics and 
> make it more
> >>  coherent, but in slightly different ways.
> >>
> >>  Either change will produce fewer inference rules and lead to less
> >>  processing in a reasoning engine.
> >>
> >>  Pat Hayes
> >>  --
> >>  
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> >>
> >>
> 
> 
> -- 
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Received on Tuesday, 18 February 2003 03:32:05 UTC