Re: A Normalization Question

On Wed, 14 Jul 2004 09:26:56 -0700, Neo wrote:

>> Er, no. If you would have read beyond the first sentence you would seen
>> that I meant that nothing in a DB *is* a fact but some things
>> *represent* a fact. Big difference.

Yes, let's. :-)

> I claim the string 'brown' is a fact. You say its not. You say "A fact
> is a true proposition." I say the string 'brown' is a true proposition
> that being: The string 'brown' is composed of the symbols 'b', 'r', 'o',
> 'w' and 'n' in that order. Or in a simpler form: 'brown' is composed of
> 'b', 'r', 'o', 'w' and 'n' in that order.

That is a fact, but it is not represented by the occurrences of the string "brown". This is demonstrated by the fact that if you remove all occurrences of the string "brown" from the database then it is still logically derivable from the contents of the database. The reason for this is of course that it is a tautology and can therefore always be logically derived, even from an empty database.

You can see how this is different from a tuple ("John", "brown") that might represent the fact that John has brown eyes. If it does and you remove this tuple from the database then (presuming there is no logical redundancy) this fact can no longer be logically derived. So in this case the occurrence of this tuple in the database does indeed represent that fact.

• Jan Hidders