Moving from DC-RDF-Taskforce list to here...
The message to which I was replying is back at
http://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=ind0603&L=dc-rdf-taskforce&P=2968
Pete
-------- Original Message --------
Subject: Re: Issue 1: Datatypes
Date: Sun, 23 Apr 2006 21:41:36 +0100
From: Pete Johnston <[log in to unmask]>
To: Mikael Nilsson <[log in to unmask]>
CC: [log in to unmask]
References: <1142954388.4333.32.camel@yossarian>
Again, picking up on something that surfaced a while ago, but which I
encountered while thinking about something else...
[snip]
> More specifically, I'd propose to
> create a special case, which is when:
>
> * The VES of the value is an instance of rdfs:Datatype (not subClass, as
> Pete pointed out)
> * There is only one value string
> * There is no language tag on the value string
> * The SES of the value string EQUALS the VES of the value.
> * There are no rich value reps
> * There are no related descriptions.
>
> Applied to the above example, we would have the following dc-text:
>
> @prefix page: <http://dublincore.org/pages/> .
> @prefix dcterms: <http://purl.org/dc/terms/> .
> @prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
>
> DescriptionSet (
> Description (
> ResourceURI ( page:home )
> Statement (
> PropertyURI ( dcterms:created )
> VocabularyEncodingSchemeURI ( xsd:date )
> ValueString ( "2002-03-04" SyntaxEncodingSchemeURI ( xsd:date ) )
> )
> )
> )
>
> mapping to
>
> page:home dc:created "2002-03-04"^^xsd:date
>
> NOTE: This of course presupposes that xsd:date is made a subClass of the
> range of dc:created.
>
> Comments?
I think it's worth highlighting a feature of Mikael's example here.
Specifically, the Voabulary Encoding Scheme URI and the Syntax Encoding
Scheme URI both use the same URI
http://www.w3.org/2001/XMLSchema#date
the URI of the XML Schema date datatype.
And that's fine because all datatypes are also classes.
In another example, that URI might occur as Syntax Encoding Scheme URI,
but the Vocabulary Encoding Scheme URI might be quite different e.g. the
value might be an Event, but I might use a Value String with that Syntax
Encoding Scheme to "represent" that Event
DescriptionSet (
Description (
ResourceURI ( page:doc )
Statement (
PropertyURI ( dc:subject )
VocabularyEncodingSchemeURI ( some:Event )
ValueString ( "The attack on the World Trade Centre on September
11, 2001" )
ValueString ( "2001-09-11" SyntaxEncodingSchemeURI ( xsd:date ) )
)
)
)
And in the context of another description the URI
http://www.w3.org/2001/XMLSchema#date might be used as a Resource URI or
a Value URI.
I think this illustrates clearly that it doesn't make sense to make
global assertions, independently of any particular statement, that some
resource "is a Vocabulary Encoding Scheme" or "is a Syntax Encoding
Scheme".
A class "is a Vocabulary Encoding Scheme" only in the context of a
statement in which the Value is an instance of that class (or maybe a
DCAP which describes some class of DC metadata description sets); and a
datatype "is a Syntax Encoding Scheme" only in the context of a
statement in which it is associated with a Value String - in some
statements (e.g. Mikael's example above) that datatype may also be a
Vocabulary Encoding Scheme; in other statements, it is not.
It seems to me we have to treat "being a Vocabulary Encoding Scheme" or
"being a Syntax Encoding Scheme" as features of the way a class or
datatype is referred to in a particular statement or DCAP, not
intrinsic, global characteristics of the class or datatype.
Pete
--
Pete Johnston
Research Officer (Interoperability)
UKOLN, University of Bath, Bath BA2 7AY, UK
tel: +44 (0)1225 383619 fax: +44 (0)1225 386838
mailto:[log in to unmask]
http://www.ukoln.ac.uk/ukoln/staff/p.johnston/
--
Pete Johnston
Research Officer (Interoperability)
UKOLN, University of Bath, Bath BA2 7AY, UK
tel: +44 (0)1225 383619 fax: +44 (0)1225 386838
mailto:[log in to unmask]
http://www.ukoln.ac.uk/ukoln/staff/p.johnston/
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