Re: Love or hate, or? domains with cardinality two

On 2015-11-06 10:40:53 +0000, compdb_at_hotmail.com said:

> On Thursday, November 5, 2015 at 3:14:51 AM UTC-8, Nicola wrote:

>> On 2015-11-05 11:08:15 +0000, Nicola said:
>> 
>>> In a relation with a boolean attribute you are effectively using a
>>> trick to encode both positive and negative information (true and false
>>> propositions), while typically in a relation schema...

Except for the fact that, by definition, the interpretation of the predicates they
appear in is constrained, i.e., it cannot be the case that P(c,true) and P(c,false)
are both true or both false.

> Your problem is you are not writing your predicates correctly.

Which predicates did I not specify correctly?

> For EM(x,b) for your first example the predicate is
> x is an employee and b and x is a manager
> or x is an employee and not b and x is not a manager
> which is
> x is an employee and it is b that x is a manager
>
> [...]
> So present tuples assert their propositions and absent tuples assert NOT their
> propositions. (Because of the second conjuct we say we are making the CWA.)
>
> So the proposition for <fred,true> is "fred is an employee and fred is
> a manager". When in the relation it asserts that and when not it
> asserts NOT that.

Ok, that's fine.

> Why do you even mention DKNY?

DKNY? Nicola

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