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Re: RDF-ISSUE-80 (rdf:PlainLiteral): Ask OWL and RIF WGs to update the rdf:PlainLiteral spec [RDF General]

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Fri, 18 Nov 2011 13:29:06 +0000
Message-ID: <4EC65DA2.6020308@epimorphics.com>
To: public-rdf-wg@w3.org


On 17/11/11 21:27, Sandro Hawke wrote:
> On Thu, 2011-11-17 at 20:32 +0000, Richard Cyganiak wrote:
>> On 17 Nov 2011, at 19:33, Sandro Hawke wrote:
>>> I think it should actually be this group which does the revision,
>>> though.
>>
>> Why?
>
> Because RDF should be the common data model.
>
> rdf:PlainLiteral was invented because a group of people trying to build
> on top of RDF found the data model just too broken to work with.   (They
> needed something simple and consistent enough on which to build
> additional logics.)  So, together with everyone who was willing to help,
> we came up with something that isn't pretty but that does work.
>
>> The rdf:PlainLiteral spec defines a datatype that's defined as being usable only *outside* of RDF graphs.
>
> That's not a design goal, it's just an aspect of how we had to define it
> to not break anything existing.    Given RDF 1.1 is willing to make some
> changes to existing things, it wouldn't necessarily have to be done that
> way any more.

s/break/change/

rdf:PlainLiteral appear very late in the OWL/RIF WG cycle.

>
>>   It defines facets for that datatype. It defines XPath functions. None of these things are directly useful for RDF. They all make sense for, and are motivated by, RIF and OWL.
>
> If you're going to actually define a useful XML datatype, it makes sense
> to define facets and XPath functions for it.   The fact that OWL 2 can
> use the facets and RIF can use the XPath functions helped motivate it,
> but it seemed like one would want these things anyway.  I mean, if you
> have a language tagged string, don't you want to be able to constrain
> and/or act upon the language tag?   So we defined a way to do that which
> happens to fit neatly into the existing XML datatype mechanisms.   They
> are in no way just for RIF or OWL -- they are for anyone who wants to
> use strings with language tags in RDF, using machinery from the XML
> world.
>
> Maybe XML is dead, so this doesn't matter any more?

XML treats language tag as an orthogonal to datatype
through xml:lang and through schema datatyping.

In that sense, RDF-2004 reflected XML quite accurately.

rdf:PlainLiteral uses a 1-D lexical space for a 2-D value space.  The 
lang tag does not have the same status as the datatype,

	Andy
Received on Friday, 18 November 2011 13:29:34 GMT

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