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

From: Jos de Bruijn <debruijn@inf.unibz.it>
Date: Fri, 27 Mar 2009 11:52:01 +0100
Message-ID: <49CCAFD1.5010605@inf.unibz.it>
To: Boris Motik <boris.motik@comlab.ox.ac.uk>
CC: public-rdf-text@w3.org, 'Jie Bao' <baojie@cs.rpi.edu>, 'Axel Polleres' <axel.polleres@deri.org>


Boris Motik wrote:
> 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.

okay, I didn't know that.  So we will not have a problem here anyway.

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

Well, there is a consensus among the people who have responded so far :-)

Jos

> 
> 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
> 

-- 
+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 10:53:05 UTC

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