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Re: So now we have tidy literals...

From: Graham Klyne <Graham.Klyne@MIMEsweeper.com>
Date: Tue, 15 Oct 2002 11:49:42 +0100
Message-Id: <5.1.0.14.2.20021015114353.00a88de0@127.0.0.1>
To: Dan Connolly <connolly@w3.org>
Cc: Brian McBride <bwm@hplb.hpl.hp.com>, RDF core WG <w3c-rdfcore-wg@w3.org>

Ah, I think I now see the crux of discussion...

In Internet protocols, there's a convention that if no language code is 
specified, then one called (something like) i-default is assumed.  (I think 
it's covered in RFC 1766, but have power cut right now so can't check 
reference.)  So I'd assumed that if a literal *can* have a language code, 
but one is not explicitly specified, then some kind of default placeholder 
is lurking in the wings.

Of course, that may not be the case.

But the distinction I was drawing was between a literal which *can* have a 
language code and a string value which (maybe) cannot.

#g
--


At 03:54 PM 10/14/02 -0500, Dan Connolly wrote:
>On Mon, 2002-10-14 at 15:55, Graham Klyne wrote:
> > Confused or no, I think we're approximately in accord.
>
>I don't think so...
>
> >  I have a slight
> > concern about "infoset" popping up in the abstract syntax, but if you mean
> > something for which an infoset could be constructed I guess that's about
> > the same.
> >
> > The words I was proposing were:
> > [[
> > An untyped literal is either a string literal or an XML literal, either of
> > which consists of a sequence of Unicode characters and a language
> > code.
>
>no, there's no language code in the literal value of...
>
>         <title>abc</title>
>
> >  See section 3.2 for details.
> > ]]
> > (noting that typed literals are dealt with in a separate, nearby section).
> >
> > This isn't meant to be a complete definition -- hence ref section 3.2.
> >
> > Personally, I'd say the xsd:string and untyped cases are different 
> (i.e. no
> > corresponding entailment).  One reason is that (I understand) an 
> xsd:string
> > value doesn't have a language.
>
>Nor does a plain (1.a) string.
>
> > #g
> > --
> >
> > At 09:34 AM 10/14/02 -0500, Dan Connolly wrote:
> > > > >> From past discussion, I'm expecting that the answer will be that a
> > > > >> literal denotes a composite value consisting of a Uniocode string, a
> > > > >> language code and an XML flag, or something of that kind.  That 
> would
> > > > >> tally with the current abstract syntax description [1].
> > > > >
> > > > >Right, though DanC has been suggesting we consider that we two 
> types of
> > > > >literals, each a pair of the literal and the string, one is a bare
> > > literal
> > > > >and the other is an xml literal.
> > > >
> > > > Yes... I think I came closer to that in the tentative text, which 
> you did
> > > > not quote.  But mainly, I wanted to make sure we're all facing the same
> > > > direction now ;-)
> > >
> > >I'm confused by the above.
> > >
> > >It seems to me that the class of Literals is a sort of union:
> > >
> > >         1.a strings, resulting from
> > >                 <title>abc</title>
> > >         where no xml:lang dominates the <title> propElt
> > >
> > >         1.b lang-strings, resulting from
> > >                 <title xml:lang="en">abc</title>
> > >
> > >         2.a XML infoset thingies, resulting from
> > >                 <title rdf:parseType="Literal">some <em>very</em> good
> > >                         stuff</title>
> > >         [some text earlier in a thread said that this was a
> > >         unicode string; I wouldn't say that; it can be serialized as
> > >         a unicode string, as we do in n-triples. But that doesn't
> > >         make it a string]
> > >
> > >         2.b XML infoset thingies, with lang, resulting from
> > >                 <title xml:lang="en"
> > >                 rdf:parseType="Literal">some <em>very</em> good
> > >                         stuff</title>
> > >
> > >         3.a datatype values, resulting from
> > >                 <date rdf:datatype="&xsd;date">2000-10-12</date>
> > >         These consist of an absolute URI reference
> > >         and a unicode string.
> > >
> > >I dunno if we have 3.b lang-datatype-values. I hope not.
> > >
> > >Nor do I know if datatype values of type &xsd;string are
> > >identical to normal 1.a strings. It seems best, for users,
> > >if they are, but it's sort of an ugly special case.
> > >
> > >Test case:
> > >
> > >         <rdf:Description rdf:about="#something">
> > >           <p1>abc</p1>
> > >           <p2 rdf:datatype="&xsd;string">abc</p2>
> > >         </rdf:Description>
> > >
> > >entails?
> > >
> > >         <rdf:Description rdf:about="#something">
> > >           <p1 rdf:nodeID="X" />
> > >           <p2 rdf:nodeID="X" />
> > >         </rdf:Description>
> >
> > -------------------
> > Graham Klyne
> > <GK@NineByNine.org>
>--
>Dan Connolly, W3C http://www.w3.org/People/Connolly/

-------------------
Graham Klyne
<GK@NineByNine.org>
Received on Tuesday, 15 October 2002 09:21:49 EDT

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