Re: SUO: Re: Proposed SUO Content Outline
"Frederick N. Chase" <fnc@mitre.org>:
>Thank you, Jon and Chris, for working with my posting.
>
>Below I'm expanding a little on what I said, in light of your comments.
>(And no doubt further exposing the unevenness in
>my understanding of our subject.)
>
>
>I was trying to further affirm the notion that,
>distasteful and complexifying though it may be,
>it will be essential for us to provide a place for
>theories, causal bubbles, axiomatizations, alternative courses,
>views, domains of interest (DOIs), viewpoints, or whatever they be
>termed
>which offer some sort of isolation one from another.
>(I recognize that some of these may be fundamentally different from
>others.)
Right, I agree this is needed. The current preoccupation with
'namespaces' in Web applications is a related concern.
>The kinds of DOIs I had in mind include the following examples,
>though I'm not sure all all of these are suitable for an
>IEEE SUO, or for a chunk that can be merged into an IEEE SUO.
Heres another, much more mundane, example. Many temporal databases
assume that time is discrete, and all durations are multiples of some
atomic time-tick (often a millisecond). Many temporal ontologies used
for physical reasoning assume, on the contrary, that time is
continuous, or at least dense. These assumptions are in direct
logical contradiction. However, the contradiction is usually harmless
in practice because no sane reasoner would use the density axiom on
an atomic time-interval; and it is easy to repair the inconsistency
by putting a protective condition on the density axiom if needed.
More seriously (and more subtly), many temporal ontologies assume
that time is the real line, but many physical ontologies (including
the SUO) use some version of the Allen interval algebra. These
assumptions are also in direct conflict. They can be reconciled, but
only at some conceptual cost; for example, by assuming that an
interval is not identical to the set of points it contains, or by
assuming that all intervals are half-open. This kind of repair work
involves a much more serious re-thinking of the overall temporal
ontology.
<snip>
>I was rejecting the "Into the Sky"/"Into the Ground" dead-end
>that Jon Awbrey and Chris Menzel describe.
This 'dead-end' is largely an illusion of Jon's, apparently due to
his not knowing anything about the state of the art in reasoning
systems. The point being that a reasoner does not (in fact, cannot
possibly) immediately infer all the valid consequences of its
knowledge, and the same machinery that enables it to detect validity
of an inference also detects inconsistencies in its own Kbase. So
they can be (and often are) written to be self-checking. Cyc is
constantly checking itself for internal contradictions, and often
finds them, without going utterly mad. (Jon is also quite wrong about
nonmonotonic reasoning, by the way, which is not a complete 'into the
sky' abandonment of consistency, but an organised way of allowing
consistency to accumulate as a result of a series of corrections to
reasonable assumptions. It needs to be treated with special care to
avoid a kind of unstable logical oscillation, but the dynamics of
this are now well understood, and there are elegant and coherent
semantic theories which account for the logical properties of such
logics.)
>Rejecting it in favor of some sort of hack involving an
>isolation-of-consequences or scoping-of-names notion and
>implicitly asking that anyone who has some idea of how to do this step
>in and
>give the idea additional legitimacy (if it deserves it).
There is an entire literature now on techniques for debugging
ontologies by rooting out latent contradictions. Can we just take
this for granted and move on?
Pat Hayes
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