# Re: Proposal: 6NF

From: Hugo Kornelis <hugo_at_perFact.REMOVETHIS.info.INVALID>
Date: Fri, 13 Oct 2006 00:26:31 +0200

On Wed, 11 Oct 2006 15:33:01 GMT, Brian Selzer wrote:

(snip)
>>>The empty set /indicates/ the absence of a value, yet it /is/ a value; a
>>>null /indicates/ the absence of a value, yet it /isn't/ a value? Why the
>>>double standard?
>>
>> Wrong. The empty set *IS* a value. It's domain is the domain of sets. A
>> set is a value that can hold zero, one or more values of a specified
>> domain. The empty set happens to hold a zero number of values.
>
>Hi, Hugo.
>
>I believe I said that the empty set *IS* a value. It's abstract, but it is
>a value.

Hi Brian,

Indeed, you did. I should have made myself clearer.

You say that, I quote, "The empty set /indicates/ the absence of a value, yet it /is/ a value". I agree that it is a value. I disagree that it indicates the absence of a value. The empty set indicates the *presence* of a value - to wit, the value {} (which, in the domain of sets, is a perfectly legal value).

If Ø is your representation of the empty set (which I usually represent as {}, two accolades with nothing in between), then this is not true. {} or Ø is a symbol that represents a value, drawn on the domain of sets. This particular value from the domain of sets happpens to have zero members in the set. It is still a set (same as 0 is still a number).

Best, Hugo Received on Fri Oct 13 2006 - 00:26:31 CEST

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