Russell Wallace wrote:
On 3/12/07, *Richard Loosemore* <[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>> wrote:
I'm not sure if you're just summarizing what someone would mean if they
were talking about 'logical representation,' or advocating it.
I'm saying there are 5 different things someone might mean, and going on
to advocate 3.5 of them while dissing 1.
For example, what about replacing this:
[Meaning #2]
edge(point(4, 5), orientation(3.7))
estimated-depth(point(87, 9), 120.4)
convex(line#17)
chair(object#33)
...etc
with this:
[Meaning #2(A)]
regularity_A1, regularity_A27, regularity_A81 ....
regularity_B79, regularity_B34, regularity_B22 ....
....
To what purpose? My version is easier to understand and debug, what
advantage does your version have?
The advantage is in the later consequences.
So what is the "regularity finding mechanism"? Well, it is not well
defined at the outset: it is up to us to investigate and discover what
regularity finding mechanisms actually produce useful elements. We
should start out *agnostic* about what those mechanisms are. All kinds
of posibilities exist, if we are open minded enough about what to
consider.
Of course. That's why we need a flexible, general-purpose representation
that can work with lots of different kinds of mechanisms.
Where do "logical representations" sit in all of this? In the case of
human systems, they appear to be an acquired representation
What of it? Just because birds are feathered doesn't mean aeroplanes
have to follow suit.
That argument comes up a lot, and generally I just ignore it because
it's too general to be a proper target for demolition, ...... but having
said that, what about: (1) So far, the aeroplanes aren't getting off the
ground, (2) The Wright brothers spent a huge amount of time studying
natural flight first, (3) Even the simplest of the "feathered" variety
of AI system are displaying intriguingly powerful properties.
what
good would it do us to start out by throwing away our neutrality on the
"what is a regularity" question and committing straight away to the idea
that a regularity is a logical atom
I didn't advocate that.
and the thinking mechanisms are a
combination of [logical inference] + [inference control mechanism]?
Not only did I not advocate that, I called it a classic mistake.
But we need to commit to some representation. It's like XML. XML gets
criticized for not being the solution to all problems, but the critics
miss the point: it's only intended to solve one problem, that of every
program using its own opaque proprietary format.
This is puzzling, in a way, because this is my ammunition that you are
using here! That is exactly what I am trying to do: invent an AIXML.
I am a little baffled because you agree, but think I am not trying to do
that....
We've got the same sort of problem here. You agree any system displaying
a significant degree of intelligence will need lots of different
modules, using different kinds of algorithms, with no way to enumerate
them in advance. Yet the modules need to work together (otherwise you
don't have a system, merely a catalog). To do that they need a shared
data representation. That representation needs to be decided before many
modules are written. Agreed so far?
If so, what else would you use? Strictly speaking, there is (in the
Turing sense) no more powerful data representation than logic, because
logic can represent anything. So we move on to pragmatic issues.
Pragmatically, logic is well understood, concise, flexible, easy to
debug, easy for lots of different kinds of modules to work with. Decades
of hard work have failed to find anything better. If you've got
something better, I'm all ears. If not, what's your objection?
It is hard to answer this battery of questions without sending you an
entire book that I don't have the stomach to write (see note below), so
now I am in a quandary.
Overall: there is such a gulf between your way of thinking and the one I
just outlined that it is hard to communicate. For example, I just *did*
describe something better! But you did not recognize it as such, so now
I am at a loss.
But more specifically, your statement that "there is (in the Turing
sense) no more powerful data representation than logic, because logic
can represent anything" is just ... loaded with assumptions, and too
general to be of any use. This is rather like saying "there is no more
powerful way of building intelligent systems than out of atoms, because
atoms can be used to build anything." Well, ...... yes, in a sense, but
at the level I am operating at, it means nothing.
Illustration. When the connectionists first came along, one of the
first things they did was build a simple network system that could model
the process of recognizing the difference between sonar echoes coming
back from rocks and from artificial objects. People had tried to build
such systems before, because human sonar operators are extremely skilled
and therefore hard to train. Their attempts to build "logic-based" AI
systems, in which things were represented in the clear way you seem to
imply above, to do the task were not much good.
But when the connectionists built a stupidly simple backprop net to try
the same task, the thing learned quickly to go well beyond the
performance of the human operators.
What was the representation that the net was using? Was it that thing
you described as the "the most powerful data representation" which "can
represent anything"? Not likely: it was a bunch of stupid
regularity-capturing elements (of the sort I described above), whose
exact interpretation was completely opaque.
There was nothing "logic-like" about that representation, but it worked
better than anything else.
This is only the tinest example: my broader point is that this lesson
extends in so many ways .... too many to sit down now and write them all
out. Others have done that kind of job (see McClelland and Rumelhart's
PDP volumes from 1986/7 for one entry point into the literature), but it
is too massive for me to do here.
Richard Loosemore.
P.S.
When I say that I don't want to write that book, I mean I don't want to
waste my time writing a complete destruction of the logic-based
representation paradigm. I prefer to be more constructive and write a
complete account of a more viable alternative, and just leave the
logic-based idea to die of its own accord. What I am doing is producing
that more positive account.
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