Re: Frames are (almost) enough for EDI
phayes@cs.uiuc.edu (Pat Hayes)
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Date: Tue, 20 Sep 1994 13:04:38 +0000
To: cg@cs.umn.edu, edi-new@tegsun.harvard.edu, srkb@cs.umbc.edu
From: phayes@cs.uiuc.edu (Pat Hayes)
Subject: Re: Frames are (almost) enough for EDI
Cc: fritz@rodin.wustl.edu, pdoudna@aol.com
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At 6:44 AM 9/20/94 -0500, Fritz Lehmann wrote:
>Michael Laing wrote on the list edi-new@tegsun.harvard.edu:
>---begin quote---
>I think an interesting area to explore is the construction of protocols whereby
>'frames' can be interchanged. A related question is: are 'frames' sufficiently
>general - this may perhaps be answered (approximately!) in a practical sense by
>looking at well-defined & useful information objects like those in legacy EDI,
>OpenDoc, RFC822 mail (easy), POP, SMTP, etc., and modelling them in 'frames'.
>Furthermore, can such protocols: preserve the generality of 'frames' and be
>syntactically expressed in ways that are: easy to process and 'extensions'
>(loosely) of existing practice (to promote acceptance).
>And would they be useful?
Questions about the expressive power or otherwise of "frames" were answered
in an old paper of mine which pointed out that all frame notations and
semantic-network systems such as "Conceptual Graphs" are notational
variations of some subset of first-order predicate logic. This was not a
deep result, let me modestly add, and has been accepted in AI as kind of
obvious now for about a decade. Some people prefer object-based notations,
or graphical notations such as "conceptual graphs" for perfectly valid
computational reasons or 'naturalness', or because of a philosophical
committment to the legacy of C.S Peirce, but none of these notations have
any *expressive* abilities which go beyond those of ordinary first-order
logic.
I agree with Fritz that the key issue is finding the right axioms, not
choosing the language to write them in. We can translate back and forth
between different formalisms pretty easily (with a little logical
ingenuity) but where we all get stuck is in saying what it is we want to
have translated.
However, long experience suggests that the idea of there being a single
correct real-world ontology is overoptimistic. Almost any concept you can
think of, even very 'basic' ones, can be described perfectly correctly in
several different incompatible ways. I am just finishing a survey of ways
of describing time, for example, which gives at least three fundamentally
incompatible views of the structure of the timeline, each with several
subcases; and each of these can be axiomatised in various ways, with
different collections of relations and objects. Is this one ontology or
several ontologies? When we get to such things as a purchase-order, the
number of ways it can be described probably runs into four or five figures.
This is one of the problems with the formalisms we have, I think: they
force one to take a stance on issues which are not really important to the
task in hand and which later get in the way. (Is a fitted carpet IN a room
or PART OF the room? How about the paint on the wall?) "Contexts" are often
cited as a way to solve this problem, but I havnt yet seen a convincing
account of how information is allowed to move between contexts, which is
this same problem in a different guise.
Pat Hayes
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