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

On Mon, 2 Nov 2015 18:29:54 +0100, Nicola <nvitacolonna_at_gmail.com> wrote:

>Not long ago, I had a quick chat with a logician, where we talked about
>boolean domains (domain with two elements) in connection to logic and
>databases. All started from an instance of a relational schema:
>
>Employee(id, dept, mgr?)
>
>where mgr? is boolean. A tuple (x,y,true) means that employee x belongs
>to department y and x is a manager of y. A tuple (x,y,false) means that
>employee x belongs to department y but x is not a manager of y.
>
>I was arguing about how schemas like that are commonly found in
>practice, and about how I feel uncomfortable with them, because, let
>apart the obvious difficulties with enforcing some integrity constraints
>(e.g., a department should have one and only one manager at a time) in

     Invalid assumption. I do some inventory counting and have seen references in stores to co-managers. The store has more than one store manager (not just managers of different ranks).

     And what obvious difficulties?

[snip]

Sincerely,

Gene Wirchenko Received on Tue Nov 10 2015 - 00:33:52 CET