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Re: Reworked sections on datatypes and literals

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Thu, 31 Oct 2002 10:36:51 +0200
Message-ID: <010e01c280b8$a9748a00$6d9316ac@NOE.Nokia.com>
To: "RDF core WG" <w3c-rdfcore-wg@w3.org>, "ext Graham Klyne" <GK@NineByNine.org>

A few comments:

1. You say 

   "RDF uses the datatype abstraction defined by XML Schema Part 2: Datatypes."

I think it is better to say 

   "RDF uses a datatype abstraction compatable with XML Schema..." 

since RDF datatyping does not include everything defined by
XML Schema, and we don't need nor want to create tighter dependendencies 
with other specs than we need to. RDF Datatyping is not XML Schema
Datatypes. It's simply compatable with XML Schema Datatypes.

2. Regarding rdfs:XMLLiteral, it reads

   "With one exception, the datatypes used in RDF have a lexical space 
    consisiting of a set of strings. The exception is rdfs:XMLLiteral, whose 
    lexical space is a set of pairs of strings and language identifiers, and 
    the value obtained through its datatype mapping depends on the language

Is this exception for XML literals really justified? If we are supposed to
treat XML literals the same as any other kind of literal, why not disregard
the xml:lang scope for them as well? Especially since it is straightforward
to define an xml:lang value for the XML literals directly. I.e., they are
literals within the RDF/XML instance, not part of the RDF/XML instance itself.
The fact that they happen to also be XML should not cause them to be infected
with syntactic machanisms specific to the RDF/XML serialization.

3. Could you expand

   "The predefined XML Schema datatypes [XML-SCHEMA2] are expected to be 
    widely used for this purpose."

to something akin to

   "The predefined XML Schema datatypes [XML-SCHEMA2] are expected to be 
    widely used for this purpose; though one is not limited only to the
    predefined XML Schema datatypes nor to XML Schema defined datatypes 
    in particular. Any datatype which conforms to this specification may 
    be used."

4. The statement

   "XML Schema Datatypes [XML-SCHEMA2] provides an extensibility framework 
    suitable for defining new datatypes for use in RDF."

suggests that RDF will understand XML Schema datatype specifications in some
manner. Perhaps it should be deleted. It's enough to simply say that datatypes
are not defined by RDF, and those familiar with XML Schema will know how to
define new types. This goes hand-in-hand with #3 above, which clarifies that
users *can* define and use other datatypes than the pre-defined XML Schema
simple types.


[Patrick Stickler, Nokia/Finland, (+358 40) 801 9690, patrick.stickler@nokia.com]

----- Original Message ----- 
From: "ext Graham Klyne" <GK@NineByNine.org>
To: "RDF core WG" <w3c-rdfcore-wg@w3.org>
Sent: 30 October, 2002 18:42
Subject: Reworked sections on datatypes and literals

> Starting with Brian's comments, and then employing a lot of editorial 
> discretion, I've done a major rework on the sections about datatypes and 
> literals.
> The main goal of this rework was to progressively introduce the concepts, 
> so the datatypes section has been moved ahead of literals, and the datatype 
> examples have been split across the two sections.
> The rework is attached to this message.  It's not very long -- I'm posting 
> the two sections to solicit feedback from the group, and make sure I 
> haven't distorted the intent in any way.  (There's still an issue of 
> requiring a lexical representation for each value [1] outstanding, which I 
> haven't got round to addressing yet, so please don't flame me on that just 
> yet.)
> #g
> --
> [1] http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2002Oct/0396.html
> -------------------
> Graham Klyne
> <GK@NineByNine.org>
Received on Thursday, 31 October 2002 03:36:55 UTC

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