From: Peter F. Patel-Schneider (pfps@research.bell-labs.com)
Date: 03/05/01
From: Dan Brickley <Daniel.Brickley@bristol.ac.uk> 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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