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From: bjpt@mulga.OZ (Benjamin Thompson)
Newsgroups: net.math
Subject: Re: Data compression and information theory
Message-ID: <854@mulga.OZ>
Date: Mon, 5-Aug-85 19:56:07 EDT
Article-I.D.: mulga.854
Posted: Mon Aug  5 19:56:07 1985
Date-Received: Wed, 7-Aug-85 01:03:52 EDT
References: <417@lasspvax.UUCP> <1010@mtgzz.UUCP>
Reply-To: bjpt@mulga.OZ (Benjamin Thompson)
Organization: Comp Sci, Melbourne Uni, Australia
Lines: 24

In article <1010@mtgzz.UUCP> version B 2.10.2 (MU) 9/23/84; site mulga.OZ version B 2.10.PCS 1/10/84; site mtgzz.UUCP mulga!munnari!seismo!harvard!think!mit-eddie!genrad!decvax!tektronix!uw-beaver!cornell!vax135!ariel!mtunf!mtunh!mtuxo!mtgzz!dmt dmt@mtgzz.UUCP (d.m.tutelman) writes:
>The one-bit-per-character assertion comes from an old classic paper.
>(Don't have a reference handy, but I believe it's by Claude Shannon
>himself, published in BSTJ in the 1950s or even '40s.)
>What he did was have human beings "guess" the next letter in
>meaningful (i.e. - not nonsense) English sentences. "Space" was included
>as a character.
But how much of each sentence was made available before guesses were made ?
I have two sentence beginnings for you to guess the next letter of:
1) "A" and 2) "".  In comparison to simple Huffman encodings, I don't expect
very many people to get it right within 5 guesses.

Are guesses really desirable in a compression system anyway ?  There's is
no-one to say whether the guess was right or wrong ...

An obvious argument against one-bit-per-character goes something like this :
The average word has (say) five characters, which would imply that its
information content can be represented with 5 bits.  This in turn would
imply that there are around 2^5, or 32, valid words.  Rather limited.
This is my interpretation of what one-bit-per-character means; if I have
missed something, please correct me.


Ben Thompson				seismo!munnari!bjpt