Newsgroups: comp.ai.philosophy
Path: utzoo!utgpu!watserv1!watdragon!violet!cpshelley
From: cpshelley@violet.uwaterloo.ca (cameron shelley)
Subject: Re: Just Minds and Machines this time
Message-ID: <1991Jan29.165646.17764@watdragon.waterloo.edu>
Sender: daemon@watdragon.waterloo.edu (Owner of Many System Processes)
Organization: University of Waterloo
References: <11656.9101241836@s4.sys.uea.ac.uk> <1991Jan25.022026.12999@watdragon.waterloo.edu> <16510@venera.isi.edu> <1991Jan27.185935.18038@watdragon.waterloo.edu> <16537@venera.isi.edu>
Date: Tue, 29 Jan 91 16:56:46 GMT
Lines: 122

In article <16537@venera.isi.edu> smoliar@venera.isi.edu (Stephen Smoliar) writes:
[...]
>I think we're basically on the same channel here.  I was using "meet" in the
>set-theoretic sense of intersection.  The more I think about it, I think there
>are (at least) two implications to this approach:
>
>	1.  There is the issue of whether or not, and how, the linkages can
>		be manipulated in order to achieve a meeting.
>
>	2.  There is the issue of WHERE on the linkages this meeting actually
>		takes place.
>
>In a very loose sense the first issue has to do with whether or not that
>particular point in space is well-formed, in the notion that Cam wishes
>to pursue.  Under the assumption that it IS well-formed, the second issue
>then takes on the matter of HOW it will be interpreted.  This is what I was
>trying to get at in saying that different ways of manipulating the linkages
>might lead to different interpretations:  Depending on the specific
>manipulations, the point may meet different locations on the linkage,
>itself.
>

I don't think that's too controversial.  The existence of multiple
interpretations is a time-honoured way of describing ambiguity: in
this case, there is more than one set of translations that meet the
desired point.  I would then go on to distinguish "ill-transmitted",
in which the desired point has been underdefined resulting in 
multiple points which satisfy the constraints of the transmission
(and each point may be ambiguous in its own right), from "ill-formed"
in which the transmitted constraints themselves cannot be interpreted
(by some sense of adequacy) so that no points at all have been
defined.  Note that the last notion can be quite independant of errors
in transmission.  The concern in my original post was that connectionist
architectures treat "ill-formed" as "ill-transmitted" when I don't
think this does the subject justice.  No doubt this is for the 
convenience of being able to use results from information theory
in all cases.  In dealing with interpretation in general, I think
such (0,1,plural) boundary cases are most profitably treated as
separate until evidence indicates otherwise.

Another area in which (to my knowledge) the '0' case is not treated is
theoretical phonology.  Although the 'null' symbol turns up in phonological
rules (deletion), it is never defined.  This also means that the theory
assumes there is some certain method of distinguishing the properties of
speech sound from those of other sound before phonology is invoked.
But I digress... (sorry!)

>Does the structure have to be connected?  I do not see that as necessary.  I am
>more interested in the extent to which this metaphor can be useful interpreted
>into a set of viable rules for manipulation the structure.  There is no reason
>to eliminate rules which would pull the structure apart unless it could be
>demonstrated that they led to undesirable consequences (such as, perhaps,
>an inability to recover information about where the meeting took place when
>it was finally achieved).  My own sense of aesthetics seems more inclined to
>allowing the "limbs" of the structure to be stretched or shrunken, rather than
>allowing the structure to be pulled apart;  but, as I said, I think it is more
>important to start thinking about reasonable ways to talk about the
>manipulation, itself.
>

Well, empirically, it is possible to lose information, and I don't see
any advantage in requiring the entire 'knowledge' structure to be
connected.  However, this may depend on how 'knowledge' is defined.

>Another possibility might be that the manipulations are sufficiently powerful
>that the structure can always access any point in the space.  In this case
>there would no longer be an issue of ill-formed points.  This might be a way
>in which the manipulation of the structure reflects an adjustment in
>interpretation to accommodate what might have otherwise been regarded
>as an ill-formed point.
>

Again, I see this as ignoring a potential problem.  Under-specification
may be treated in this fashion, but I still see 'non-specification' as
something that must be dealt with.  Perhaps even a further distinction
is necessary:  a system shouldn't waste time interpreting random noise
('non-transmission'), but should simply baulk at nonsense ('ill-formed'
transmission), and deal as mentioned above with noise in a sensible
transmission.  For example, the system should deal differently with:
"%^%#*%^&%^%^%%^$#@!#$#" (noise), "After being run *^@r by the truck,
the man said 'Ouch'!" (where "over" can be interpolated), "flying
airplanes make people ill" (ambiguity), and "pick peek poke pack puck pink"
(nonsense).  Should I interpret the last as a description of a
psychodelic hockey game, or just respond "What?"  I think both should
be options, but NN's (as they exist currently) do not have a choice
in such a case.

>Perhaps I can try to illustrate what I am trying to say here with a concrete
>example.  Peter Todd recently published some of his work in trying to use
>connectionism for musical composition.  The basic approach was to "train"
>a network with some examples of melodies and then, through control of some
>inputs, allow a trained network to synthesize new melodies.  During training,
>Todd has some very strict rules about what constitutes well-formed input.
>However, when he leaves the network to its own devices, so to speak, the
>results it yields do not respect those rules.  As an outside observer, he
>interprets them in a way which basically "makes sense" according to the
>original INTENT of his rules.  To return to my metaphor, in the strictest
>sense Todd's network converges to points in space which are actually
>ill-formed.  However, his human intelligence controls this metaphorical
>system of linkages in such a way that he can still assign interpretations
>to those points which are consistent with what he originally had in mind.
>Robustness is thus a matter of finding the best interpretation for a given
>situation (for some metric for "best") rather than trying to decide, in any
>absolute sense, whether or not that situation is "well-formed."

This suggests that the notion of "ill-formed" is context-dependant.  My
response in this case would be that Peter's experiment has defined away
the notion of ill-formed at the start, in the sense that the structure
of the net has been controlled so that it can only produce results which
have possible 'melodic' interpretations.  In any case, this seems to be
bringing the mountain to Mohammed; simply deforming the topology of
the knowledge structure to a point doesn't appear to me to be much
different than moving a point across the topology.  But your point is
well taken, some notion of 'systematic accomodation' seems useful.

				Cam

--
      Cameron Shelley        | "Absurdity, n.  A statement of belief
cpshelley@violet.waterloo.edu|  manifestly inconsistent with one's own
    Davis Centre Rm 2136     |  opinion."
 Phone (519) 885-1211 x3390  |				Ambrose Bierce
