Revisiting AllDisjoint (was Proposed (parital) response to Ken Laskey and questions for WG)

I would like to take a moment to see what people think about having 
to reopen this issue (or possibly move forward over an objection):

In a conversation (non electronic) with Ken Laskey, who has again 
raised the issue of having an owl:allDisjoint construct (mirroring 
the allDifferent construct), I pointed him to Dan Connolly's [1] 
earlier response to this issue.  Ken indicated that he was not likely 
to accept this answer, and in conversation he brought up many use 
cases where this would be needed.  Basically, he disputes our 
contention that since this occurs in "class space" it is likely to be 
just a small number -- as he points out,  we already have a number of 
ontologies in OWL that are quite large (the NCI ontology and the 
GALEN ontology, are two examples).  In these ontologies, there are 
numerous cases where one would want to take a large set of classes 
(for example the different kinds of cancers) and make it explicit 
that some of these are disjoint (and thus others aren't necessarily) 
-- even though N is comparatively small, say 100 (remember the total 
number of classes in NCI is about 17000), this takes ~(N^2)/2 = 5,000 
(!!) OWL statements.
   Further, Ken points out that even in some of the smaller ontologies 
we've created, the number of classes and the number of disjoint 
classes can be almost identical (for example, military ranks are 
mutually disjoint within services, but not always between - someone 
cannot be an Army Lieutenant and and Army Captain, but there are rare 
cases where someone is "dual hatted" as an Army Colonel and a Navy 
Captain, for example).  Here's the odd thing -- the number of classes 
in the military ranks ontology would be about 50 (if one includes 
officers and non-officiers), which would require on the order of 1000 
disjoint statements --significantly dwarfing the size of the original 
ontology!
  Note that in none of these use cases are we talking disjoint unions 
per se (although I suppose one could create a workaround if one had a 
disjointunion construct).
  I think the N^2 problem in the size of the ontologies we're already 
seeing might be evidence to reopen this issue.  Alternatively, if 
there is a decent workaround, we might want to document that 
workaround and not add this construct.  We can also try to move 
forward over Ken's objection, although my preference would be to look 
for a way not to.

  -JH
p.s. Please note that this would NOT require any new semantics or any 
major new syntax - semantically we already have the ability to assert 
the pairwise disjuncts, and semantically this could be done using the 
same construct we created for allDifferent.


[1] 
http://lists.w3.org/Archives/Public/public-webont-comments/2003Jun/0038.html

-- 
Professor James Hendler				  hendler@cs.umd.edu
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