From: pat hayes (phayes@ai.uwf.edu)
Date: 08/28/01
(Im sending this to the entire JC in case anyone has anything to say about it. If you aren't interested, please ignore it, thanks.) Re. today's telecon, I would like to bring up the question of the connections (or lack) between the two issues of whether 'subclass' is understood to mean proper subclass, and whether subclass loops should be illegal. I confess to having conflated these in my mind, largely I suppose because I couldn't imagine any reason to forbid subclass loops other than because 'subclassOf' is understood to hold only between proper subclasses. Since Peter, Ian and others all joined in a chorus of dismay when I said this, and since this assumption is currently embedded in the draft RDF/S model theory, I would like to pursue it a little more. 1. What reason can there be to forbid subclass loops, other than subClassOf being understood to mean proper subclass? 2. Suppose Subclass is the subclass relation, Psubclass the proper-subclass relation, and R is any binary irreflexive relation between classes; then (R intersect Subclass) = (R intersect PSubclass). From which is follows that if some formal relation symbol on classes is loop-free, then if it can be interpreted as meaning subclass then it can also be interpreted as meaning proper subclass, without changing the truthvalues of any expressions in the language. So, what justification can there be for asserting that rdfs:subClassOf does *not* mean proper subclass? Thanks for any input/feedback. As the RDFCore WG is on the very edge of adopting the model theory as a working draft, i would greatly appreciate any feedback asap, so we don't go public with a major bug. Pat --------------------------------------------------------------------- (650)859 6569 w (650)494 3973 h (until September) phayes@ai.uwf.edu http://www.coginst.uwf.edu/~phayes
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