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RE: Further changes to rdf:text + a proposal for a change

From: Boris Motik <boris.motik@comlab.ox.ac.uk>
Date: Fri, 27 Mar 2009 10:41:24 -0000
To: "'Jos de Bruijn'" <debruijn@inf.unibz.it>
Cc: <public-rdf-text@w3.org>, "'Jie Bao'" <baojie@cs.rpi.edu>, "'Axel Polleres'" <axel.polleres@deri.org>
Message-ID: <667ADF610B80433A980FBA8AE0140714@wolf>
Hello,

Unless I've misunderstood something, I don't think that plain RDF literals can
have empty language tags: according to BCP-47 (as well as the older RDF 3066
cited by RDF), an empty string is not a language tag.

So does this mean we have a consensus for this change? Can I just go and
implement it?

Regards,

	Boris

> -----Original Message-----
> From: Jos de Bruijn [mailto:debruijn@inf.unibz.it]
> Sent: 27 March 2009 10:31
> To: Boris Motik
> Cc: public-rdf-text@w3.org; 'Jie Bao'; 'Axel Polleres'
> Subject: Re: Further changes to rdf:text + a proposal for a change
> 
> 
> > Another problem is in the treatment of xsd:string. The old version of the
> > document said that implementations MAY choose to make the value space of
> > xsd:string be a subset of rdf:text. I believe that MAY should actually be a
> > MUST. Without this, we could get into the following situation:
> >
> > - The typed RDF literal "abc@"^^rdf:text would be interpreted as ("abc","").
> > - Type plain RDF literal "abc" would be interpreted as "abc".
> > - Clearly, the two literals would NOT be the same.
> > - However, the typed RDF literal "abc@"^^rdf:text would be replaced with the
> > plain RDF literal "abc", which would suggest that the two literals ARE the
> same.
> 
> it seems to me that this shortcut syntax should not be allowed if we go
> for the MAY option.
> 
> >
> > This seems seriously flawed. Consequently, I have changed a MAY into a MUST.
> 
> I'm not so sure that I like this.  We would require specifications that
> want to use rdf:text to interpret the string datatypes in a nonstandard way.
> 
> >
> > There is, however, a much nicer solution to the latter problem. We could
> change
> > the value space of rdf:text such that it contains two types of objects:
> >
> > - all strings, and
> > - all pairs of the form ( s, l ) where l is a (nonempty) language tag.
> 
> I like this solution.  The only potential drawback I see is that we
> cannot express plain literals with empty language tags, but I don't
> think it is a serious issue.
> 
> >
> > In this case, rdf:text would *be* interpreted as the set of all plain RDF
> > literals. That is, we would not need to fuss about with changing the
> > interpretation of xsd:string: the very definition of the value space of
> rdf:text
> > would contain the value space of xsd:string, as well as all plain RDF
> literals.
> > Thus, we could just simply note this in the document and would not need any
> > additional definitions. Furthermore, the XQuery functions that work on
> > xsd:string would be readily applicable to the subset of rdf:text that does
> not
> > represent strings with language tags.
> >
> > The nice aspect of this solution is that rdf:text then just provides an
> explicit
> > name for the set of all plain RDF literals, so we can't really be accused of
> > changing anything.
> >
> > The only downside is that the definitions of facets and some functions would
> > become slightly messier, as they cannot treat literals with and without
> language
> > tags uniformly any more. I think, however, that this is a small price to pay
> for
> > the elegance that this solution brings.
> 
> Indeed a very small price to pay.
> 
> 
> Best, Jos
> 
> >
> > Please let me know how you feel about this. If everyone agrees, I would like
> to
> > make the change as soon as possible (preferably today) so that the document
> can
> > be reviewed soon.
> >
> > Regards,
> >
> > 	Boris
> >
> 
> --
> +43 1 58801 18470        debruijn@inf.unibz.it
> 
> Jos de Bruijn,        http://www.debruijn.net/
> ----------------------------------------------
> Many would be cowards if they had courage
> enough.
>   - Thomas Fuller
Received on Friday, 27 March 2009 10:42:38 UTC

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