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From: aweinste@diamond.bbn.com.UUCP
Newsgroups: comp.ai,comp.cog-eng
Subject: Re: The symbol grounding problem
Message-ID: <6211@diamond.BBN.COM>
Date: Thu, 28-May-87 20:46:47 EDT
Article-I.D.: diamond.6211
Posted: Thu May 28 20:46:47 1987
Date-Received: Sat, 30-May-87 05:45:45 EDT
References: <764@mind.UUCP> <768@mind.UUCP> <770@mind.UUCP> <6174@diamond.BBN.COM> <786@mind.UUCP>
Reply-To: aweinste@Diamond.BBN.COM (Anders Weinstein)
Organization: BBN Laboratories, Inc., Cambridge, MA
Lines: 41
Keywords: icons, categories, symbols, grounding
Xref: utgpu comp.ai:426 comp.cog-eng:99

Replying to my claim that 
>>	                                ...loss of information, i.e.
>>	non-invertibility, is neither a necessary nor sufficient condition for 
>>	analog to digital transformation.

in article <786@mind.UUCP> harnad@mind.UUCP (Stevan Harnad) writes:
>
>The only point that seems to have been clearly made in the sizable discussion
>of the A/D distinction on the Net last year (to my mind, at least) was that no
>A/D distinction could be agreed upon ...
>
>In the discussion to which you refer above ...  the issue was not the A/D
>transformation but A/A transformations: isomorphic copies of the
>sensory surfaces. These are the iconic representations. So whereas
>physical invertibility may not have been more successful than any of
>the other candidates in mapping out a universally acceptable criterion
>for the A/D distinction, it is not clear that it can be faulted as a
>criterion for physical isomorphism.

Well the point is just the same for the A/A or "physically isomorphic"
transformations you describe.  Although the earlier discussion admittedly did
not yield a positive result, I continue to believe that it was at least
established that invertibility is a non-starter: invertibility has
essentially *nothing* to do with the difference between analog and digital
representation according to anybody's intuitive use of the terms.

The reason I think this is so clear is that for any one of the possible
transformation types -- A/D, A/A, D/A, or D/D -- one can find paradigmatic
examples in which invertibility either does or does not obtain.  A blurry
image is uncontroversially an analog or "iconic" representation, yet it is
non-invertible;  a digital recording of sound in the audible range is surely
an A/D transformation, yet it is completely invertible, etc.  All the
invertibility or non-invertibility of a transformation indicates is whether
or not the transformation preserves or loses information in the technical
sense. But loss of information is of course possible (and not necessary) in
any of the 4 cases.

I admit I don't know what the qualifier means in your criterion of "physical
invertibility"; perhaps this alters the case.

Anders Weinstein