[crm-sig] Re: CRM version 3.2

Nicholas Crofts nickcrofts at yahoo.com
Fri Jul 13 15:22:32 EEST 2001


Dear all,
I have no objections to the modifications in version
3.2 needed to avoid the recursion problem. 

However, I didn't find Martin's explanation very clear
so I shall try to reexpress the notions in my own
terms - Martin please shout if this is not what you
intended. 

The "Beginning of Existence" and "End of Existence"
classes are high level classes which are linked
directly to the top level class E1 CRM Entity. This
means that they can be linked to instances of
themselves: the beginning of the beginning of the
beginning of the end of the end of the end.... i.e. a
recursion. I'm not clear about why recursive linking
of this sort is a problem, since the recursion is not
forced. If every instance in the CRM *must* have a
beginning, then we obviously have big problems, since
the regression becomes infinite. Talking about the
beginning of the end or the end of the beginning, on
the other hand, is sometimes appropriate.

Be that as it may, I understand that Martin proposes
as a solution the introduction of a new high level
entity 'existence' which breaks the recursion loop.

Martin, can you explain please exactly *how* the
recursion loop is split by the new entity and where it
sits in the hierarchy. (Reference to the relevant
property links... etc.) 

Thanks

Best wishes

Nick Crofts (pp Disgusted, Tunbridge Wells ;-)



 --- martin <martin at ics.forth.gr> wrote: > Dear All,
> 
> Just to avoid an outcry of disgust about the change,
> I send you
> the version 3.2 for a fast check. We have corrected
> further errors
> in the graphics, two missing declarations of what a
> short-cut is 
> about ("has section", and "took place on or
> within"). Note that 
> all short-cuts are explained in this document.
> 
> Now here the remedy for the recursion problem (also
> in the introduction
> to version 3.2):
> 
> The Agios Pavlos Extensions declared two new
> abstract entities: "Beginning of Existence" and "End
> of
> Existence" as fundamental building blocks for
> temporal and spatiotemporal reasoning. In particular
> 
> they support the analysis of the concepts "terminus
> postquem" and "terminus antequem",
> fundamental to historical studies. The range of the
> respective links " brought into existence",
> "took out of existence" has been declared in lack of
> a more precise notion as "E1 CRM Entity". 
> This causes a recursion on the concept itself, and
> on all events and activities below. 
> E.g. a Destruction was brought into existence etc.
> Therefore the abstract entity Existence has 
> been declared in agreement with the scope note of
> "Beginning of Existence", which seems to perfectly 
> capture the notion, and avoids the recursion by
> unwanted inheritance, and the
> underspecification problem of the range entity. Even
> though the introduction of a high-level 
> entity may seem to be a big step, it is
> conservative: No current instances are invalidated. 
> It is further an abstract entity, not intended for
> instantiation. It's effects are local,
> i.e. restricted to the immediate subclasses and
> superclasses of "Existence". 
> 
> The entity Existence "exists" since 1992 in the CLIO
> system at the museum Benaki.
> 
> Martin
> -- 
> 
>
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>    Foundation for Research and Technology - Hellas
> (FORTH)   |
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-------------------------------------------------------------- 

=====
Nicholas Crofts
DAEL / DSI
rue David-Dufour 5
Case postale 22
CH - 1211 Genève 8
tél +41 22 327 5271
fax +41 22 328 4382

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