- From: Frank Manola <fmanola@mitre.org>
- Date: Tue, 04 Sep 2001 11:10:50 -0400
- To: Dan Brickley <danbri@w3.org>
- CC: w3c-rdfcore-wg@w3.org
Dan-- I agree that folks who *design* schemas with explicit subclass loops are probably making an error of some kind. But another use case here is when some of the class (subclass) relationships are *derived* (e.g., the inference mentioned in the snippet from the forwarded message below). For example, in Semantic Web apps I may be combining information based on a number of different schemas, and while the individual schemas may contain no loops, the combination may turn out to (effectively) have one. Rather than throwing out the resulting "effective schema" as violating some syntactic constraint, I want to determine what having come up with that loop "means". I could still conclude that an error had been made, but I might also conclude that the classes involved in the loop were equivalent (and the designers of the individual schemas just hadn't known about the other ones). --Frank Dan Brickley wrote: > > FWIW I've no objections to making the change. I still thing that folk > designing schemas with subclass loops are making a usability error, but am > quite happy with the idea of removing this constraint from RDFS itself. > > Dan > > ---------- Forwarded message ---------- > Date: Mon, 03 Sep 2001 22:56:16 +0200 > From: Frank van Harmelen <Frank.van.Harmelen@cs.vu.nl> snip > > In more detail: > > 1. in DAML+OIL, subclass-relations can be inferred even if they are not > explicitly stated (note that this is an important difference from RDF-S, > where A is only a subclass of B if >*and only if*< it is either > explicitly stated, or follows from subsumption in the class-hierarchy). > -- Frank Manola The MITRE Corporation 202 Burlington Road, MS A345 Bedford, MA 01730-1420 mailto:fmanola@mitre.org voice: 781-271-8147 FAX: 781-271-8752
Received on Tuesday, 4 September 2001 11:11:27 UTC