Re: Pizza Example

From: Anthony W. Youngman <>
Date: Thu, 22 Apr 2004 00:50:20 +0100
Message-ID: <>

In message <>, Tony <> writes
>> I do appreciate what you're saying, about how database integrity
>> standards are rigorous, but the scientific equivalent of what you
>> propose is not separating the results into "90% good, 10% bad"; it is
>> claiming that you have just invented a perpetual motion machine. In the
>> The standard version of the law is basically "in any closed system, any
>> change will increase entropy". A physicist would also recognise and
>> accept the following paraphrase - "in any closed system, any change will
>> destroy information" - the terms "entropy" and "information" are
>> recognised as a sort of opposite (I can't remember the detail, it's too
>> long ago).
>So am I right in thinking that you do not believe (as it appeared
>earlier you did) that normalisation by non-loss decomposition loses
>information always? Rather you are saying that mistakes could be made
>while storing data such that some small fraction of the data would
>lose its correct linkage? Is that your position? If so it is a lot
>less ridiculous than I previously thought, while being typically
>irrelevant to the topic. By extracting the data from the real world
>and storing it in ANY database (even Pick) you are changing it in some
>sense, and the chance of errors exists. So what?

I've actually managed to work out a formal statement of what I always suspected.

"Normalisation by non-loss decomposition" is impossible. The law of entropy says so.

So, to rephrase your last sentence, "By extracting the data from the real world and storing it in ANY database you are changing it in some sense, and losing data IS INEVITABLE."

The more you change it, the more you lose. And the more you decompose it, the closer you get to the point where "cause and effect" ceases to have meaning :-) (which means it gets more and more likely, that an attempt to get back to where you started will leave you somewhere else entirely :-)


Anthony W. Youngman - wol at thewolery dot demon dot co dot uk
HEX wondered how much he should tell the Wizards. He felt it would not be a
good idea to burden them with too much input. Hex always thought of his reports
as Lies-to-People.
The Science of Discworld : (c) Terry Pratchett 1999
Received on Thu Apr 22 2004 - 01:50:20 CEST

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