dawn wrote:
> JOG wrote:
>
>>Brian Selzer wrote:
>>
>>>"JOG" <jog_at_cs.nott.ac.uk> wrote in message
>>>news:1159954091.119164.155490_at_m73g2000cwd.googlegroups.com...
>>>
>>>>All of your points represent a wild goose chase in my eyes Brian. A
>>>>proposition with a NULL in it is no proposition at all. From a logical
>>>>perspective, case closed. A relation tuple with a NULL in it is no
>>>>relation tuple at all. From a mathematical perspective, case closed.
>>>>Trying to invoke the 'kludge perspective' is hardly going to convince a
>>>>theoretical newsgroup.
>>>>
>>>
>>>Is the empty set a value? Yes, it is. So why can't a null be?
>>
>>Because an empty set is a value and a NULL is not.
>
>
> This is entirely a matter if definition. I have worked with "NULL
> values" and with an SQL NULL. The first is a value. The way it might
> be handled in a 2VL language that works with such values could be
> modeled with the empty set. If you are talking about the SQL NULL or
> if you define the relational model to include 3VL (which it seems many
> theorists do not), then a NULL is defined as a non-value.
>
> So, your above statement is entirely about the definition of NULL,
> right?
>
> Given the definition of NULL that I typically use (with non-SQL based
> solutions), NULL is a value and can be modeled mathematically with the
> empty set. In that case, a relation tuple with a NULL is as valid
> mathematically as one without. Agreed? --dawn
Well, if it's merely a matter of definition, then, "No. Not agreed."
Received on Fri Oct 06 2006 - 20:31:36 CDT
