Re: viewpoints and multiple inheritance.
Title: Re: viewpoints and multiple
just finished reading the recent messages (it took a while, and I
haven't attacked the huge discussion on PSL yet...), and I'd like to
post some comments. I'll try to use ONE message per topic, with a
clear subject line. I encourage everybody to do the same, going
through this mass of messages was not easy...
At 1:06 AM -0400 20/5/2000, Patrick Cassidy wrote:
(2) Will multiple inheritance be
allowed? Although it may be
avoidable in theory, it seems to conform to the intuitive
most people have
about class membershiop, and it may be the only
way that different groups with different viewpoints will agree
a single upper
ontology. I vote for multiple inheritance.
I definitely agree on allowing multiple inheritance in general,
but some caution is needed with different viewpoints. I am not sure
what Pat had in mind here, but suppose that a castle, for instance,
is seen as a kind of building under a certain viewpoint and as a
bunch of bricks under a different viewpoint. A possible way of
modeling this situation is by admitting that the concept
"castle" specializes both "building" and
"bunch of bricks". Using IS-A links to represent multiple
views is indeed a common habit.
The problem however is that the concept "building" has
some properties that are incompatible with those of "bunch of
bricks". For instance, we usually admit that a castle must
possess a particular shape (more or less) in order to exist, while
there is no similar requirement for the bunch of bricks. In other
words, having a certain shape is "essential" for the castle
and not essential for the bunch.
In this case, modeling multiple views by means of mutiple IS-A
links is simply *wrong*, because it leads to an inconsistent theory.
Rather, two different (micro)theories may be built, reflecting the
Some years ago, I remember a discussion about this issue with
CYC people. As far as I remember, a wooden table in CYC is seen at
the same time as a piece of wood and an artifact.
I have been working hard on this problem in the recent years,
and, together with Chris Welty, I have just finished a paper which
offers some principled tools for addressing modeling problems like
Towards a methodology for ontology-based
This is a simplified and updated version of some previous work,
which I believe can be of great help for verifying the
"well-foundedness" of taxonomic structures.
National Research Council
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