Re: [RIF-RDF] (potential) issues regarding correspondence of identifiers

Jos de Bruijn wrote:

>>> There are some further differences between the specification
>>> of the string datatype in XML schema 1.0 and XML schema 1.1; in the
>>> former case, the datatype is based on the Char production in XML 1.0; in
>>> the latter case, the datatype is based on the Char production in XML 1.1.
>>> An important question is what to do with plain literals which contain
>>> characters which are not in the lexical space of xsd:string.
>> So there is a real difference there. XML 1.0 does not allow characters
>> like BEL (those below #x20 other than #x9 #xA and #xD) XML 1.1 does
>> allow those characters.
> 
> Are these characters (i.e. those below #x20 other than #x9 #xA and #xD)
> actually Unicode characters?

Yes, though they are control characters rather than displayable characters.

Note that even though the XML1.1 spec allows them in the Char production 
it "discourages" them:

[[[
Document authors are encouraged to avoid "compatibility characters", as 
defined in Unicode [Unicode]. The characters defined in the following 
ranges are also discouraged. They are either control characters or 
permanently undefined Unicode characters:

[#x1-#x8], [#xB-#xC], [#xE-#x1F], ...
]]]


>> Since the only normative exchange syntax for RIF and for RDF is XML then
>> it is not actually possible to exchange characters sequences other than
>> those expressible in the XML version one is dealing with. So we just
>> have to be clear which version XML RIF is based on.
> 
> It is always possible to define an embedding, but of course it would be
> ideal if strings can be exchanged as such.
> 
>> The most general solution is perhaps to say that the we regard the value
>> space of xsd:string being that defined in XML 1.1. Exchange using XML
>> 1.0 is entirely legal and permitted but the lexical space is then
>> restricted slightly.
> 
> I guess this is reasonable, because XML schema 1.1 has last call working
> draft status.

Quite so, we're not that close ourselves :-)

Dave
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Received on Monday, 3 September 2007 12:12:14 UTC