Re: More Work on iCalendar RDF Schema

(+cc: Brian McBride, RDF Core WG co-chair)

On Tue, 26 Jun 2001, Libby Miller wrote:

> > > route we chose to add this feature. This does seem like a
> > > somewhat tricky issue you're facing.  The best way I can think
> > > of is something like:
> > >
> > > 	<dtstart><DateTime rdf:value="W3CDTF goes here" /></dtstart>
> > >
> > > What do you think?
> >
>
> this would be a good option - but I prefer Jan's _if_ this work  is
> likely to happen reasonably soon!

In the RDF Core WG we are about to start opening up issues relating to the
RDF Schema Specification. Input from real-world applications of RDF, such
as rdf-calendar, is of great value: it helps us prioritise our work, so we
can focus on removing obstacles to RDF deployment. It also provides us
with test cases material, so we can have some metrics for judging success.
>
> what d'you reckon Jan? Is there anything I/we can do to speed this
> up? (these issues keep cropping up) I've got project time I could use
> to look at this issue.

The most detailed work on this to date has been in DARPA's DAML
initiative. See http://www.daml.org/2001/03/daml+oil-index.html for
recent specs which include a proposal for doing datatyping in RDF, or
http://www.w3.org/RDF/Interest/ -> http://lists.w3.org/Archives/Public/www-rdf-logic/
for the RDF-Logic mailing list where many of the DAML folk hang out.

The reference description of March's DAML+OIL spec has this to say on
datatyping of literals using XML schema datatypes:

http://www.daml.org/2001/03/reference.html#Values
[[
Datatype values are written in a manner that is valid RDF syntax, but
which
is given a special semantics in DAML+OIL.
The preferred method is to give a lexical representation of the value as a
string, along with an XML Schema datatype that is
used to provide the type of the value as well as the parsing mechanism to
go from the string to the value itself.
The XML Schema datatype is the rdf:type of the value, and the
lexical representation is the rdf:value of the value.
So the decimal 10.5 could be input as
<xsd:decimal rdf:value="10.5">
provided that xsd was defined as the URI of the XML Schema
Datatype specification.
As a nod to backward compatability, literals that occur outside this sort
of construction are interpreted as any of the XML Schema Datatype values
with this lexical representation.  These values are mostly unusable unless
some typing information is available, such as a range for a property.
The question of whether any XML Schema datatype can be used in such
constructions, or whether only certain XML Schema dataypes can be so used
(such as only the predefined datatypes), remains open.
]]

> Are there any RDF processing issues you know of about this change?
>
> what does everyone think?

I suggest trying to implement according to the DAML+OIL proposal, and
letting the RDF Core WG know if it works, or doesn't work, for calendar
applications. This will provide useful fodder for RDF Core discussions
when we get to this topic.

Dan


>
> Libby

Received on Tuesday, 26 June 2001 07:25:51 UTC