Re: Pizza Example

In message <slrnc7umpn.l4q.choess_at_force.stwing.upenn.edu>, Chris Hoess <choess_at_stwing.upenn.edu> writes
>In article <TVoj+7HXgvfAFwwt_at_thewolery.demon.co.uk>, Anthony W. Youngman wrote:
>>
>> (And I'm not against maths. It's just that science is all about fuzzy
>> logic, uncertainty, and statistics. But (a) my grasp of the fundamental
>> theory behind that is very poor, and (b) it seems to be a lot better
>> than anybody else who might be inclined to debate with me. I'm just
>> looking for *scientific* proof, not mathematical, that relational theory
>> works, and nobody seems willing to try to prove it.)
>
>I'm not sure asking for "scientific" proof of something that's not a
>scientific theory makes sense. Newtownian mechanics offers rules by which we
>can describe the world. The relational model offers rules for the
>manipulation of propositions, whose mapping to the real world is arbitrary
>(but should be consistent for each individual database). I suppose I might
>try to put the premises of the relational model thus:

I know what you're saying. But that is confirming that relational theory is a branch of *pure* mathematics. As such, you are admitting that you have no evidence that it has any relationship whatsoever with the real world - and if that is the case what on earth is the point of trying to model the real world using it?!

I've got no problems admitting that relational is very good, consistent model. Where I *do* have a problem is the belief by so many people that it is the right model for the real world. And proving that lies in the realms of *science*, not maths. (Yes, the dividing line between "applied maths" and "experimental science" is very blurred, but until you can convince me that there is more to relational theory than Pure Maths, I'll continue asking for evidence as to relational's relevance to the real world.)
>
>Axiomatic statements about the world form the conditions of the database.
>Data consists of statements which are evaluated as logical propositions
>against the constraints.
>Queries against the database consist of the application of additional
>constraints (axioms) to the propositions in the database, and return all
>logical propositions which are true in the new axiomatic system.
>
>So statements in a relational database are guaranteed to be true to the
>degree that truth can be defined by the constraints expressed in the
>database.
>
>As I see it, the main two lines of "attack" are the idea that all data can
>be represented as statements (certainly the world is fuzzy, but how
>better to *automatically* evaluate truth than logic?) and the expressive
>capabilities of the relational model as regards conditions (but here perhaps
>we run into Russell's Paradox).

Substitute "truth" with "consistency". If, by "truth", you mean "corresponds with reality", then (a) you can NOT do it automatically, and (b) logic is completely the wrong tool - after all didn't Aristotle prove that a pound of lead is heavier than a pound of feathers :-) (yes, I know I've quoted the story wrong - it was something about falling faster or something :-)
>
>I am neither by training nor practice a logician, so I'm not entirely sure
>this description is correct, but I think it's a good starting point for
>discussion of the issue.
>
By training I'm a scientist. Logic is a wonderful tool, but it should be tested by experiment ...

Cheers,
Wol

-- 
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