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RE: Cyclic Classes/Properties [was: Re: DAML Correction: Same Is Not A Sub Of Sub]

From: Peter Crowther <peter.crowther@networkinference.com>
Date: Fri, 11 May 2001 13:05:30 +0100
Message-ID: <B6F03FDBA149CA41B6E9EB8A329EB12D05A269@vault.melandra.net>
To: "'Sigfrid Lundberg, Lub NetLab'" <siglun@gungner.lub.lu.se>
Cc: www-rdf-logic@w3.org
> From: Sigfrid Lundberg, Lub NetLab [mailto:siglun@gungner.lub.lu.se]
> To put this in another way: Could the ability to say (i.e., 
> in rdf/daml) 
> that sub-titles "<" titles rather than just that sub-titles 
> "<=" titles
> make a more solid ground for inference. I mean, some statements could
> actually be more precise... I'd reckon that we need both.

"<" and "<=" here stand for subset relationships.  To expand, you are
stating that the set of all sub-titles should be a strict subset of the set
of all titles, rather than that the set of all sub-titles should be a subset
*or equal to* the set of all titles.  In both cases, any member of the set
of sub-titles is also a member of the set of titles.

Introducing a strict-subset interpretation leads to some interesting issues
that I don't know how to resolve.  In particular, you are defining that
there is a non-empty set of titles that are not sub-titles without stating
criteria for inclusion in that set.  How do you name the class corresponding
to that set?  Do you ensure that there may never be a singleton subclass of
a class (generally good modelling practise)?  And if so, what do you do
while you are developing an ontology and simply haven't fleshed that bit out
yet, but want to test it?

		- Peter
Received on Friday, 11 May 2001 08:05:57 UTC

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