Re: DAML and Dublin Core: incompatibility?

From: Peter F. Patel-Schneider (
Date: 03/05/01

From: Dan Brickley <>
Subject: Re: DAML and Dublin Core: incompatibility?
Date: Sat, 3 Mar 2001 14:55:20 +0000 (GMT)

> On Sat, 3 Mar 2001, Ian Horrocks wrote:
> > On March 2, Dan Connolly writes:
> > > Dan Brickley wrote:
> > > > This is a followup to some hallway and lunchtable conversations about
> > > > DAML datatyping and the work of the Dublin Core Metadata Initiative.
> > > >
> > > > My understanding of the forthcoming revision of DAML+OIL+DT(*) is that
> > > > we say all properties are either of the kind that point to resources, or
> > > > of the kind that point to concrete datatypes, strings structured as per
> > > > XML Schema part 2.
> > > 
> > > I don't think that's quite right; I'm not confident I know where
> > > the latest draft is, but my understanding is: DAML+OIL+DT doesn't
> > > say that all properties are either black or white; it just doesn't
> > > tell you the semantics of the grey ones.
> > 
> > This is exactly the case: DAML+OIL+DT defines two subclasses of
> > Property, AbstractProperty and DatatypeProperty.
> So I can re-assure the DC folks that DAML processors won't be throwing
> exceptions or refusing to load DC-based data structures because of this?

I don't know what you mean by throwing exceptions or refusing to load.
Just as with RDF, there is no API for DAML+OIL, so there is no notion of an
exception or loading.  

For the case of ``grey'' properties, namely those that are neither
restricted to datatype values nor to abstract objects, there is in fact a
perfctly good semantics for them in the new version of DAML+OIL.  It is
just that very little can be said about them.  In particular, none of the
advanced DAML+OIL constructs (like restrictions) can be used on these grey
properties, so their representational power is just that of RDF properties.

Peter Patel-Schneider

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