Re: FK - automatic value change when parent changes

"joel garry" <joel-garry_at_home.com> wrote in message news:9fa0cb07-904e-421f-b265-d0e5ff234981_at_g28g2000prb.googlegroups.com...
> Problem with
> classic
> relational theory, it lacks time dynamism, it's not always just
> another attribute as you discover unelocuted requirements.

Not a problem - Chris Date cracked that a few years ago with a Hugh Darwen and another persons whose name I forget. Resulted in 6th Normal form, which collapsed to 5th Normal form in the absence of timedependency  and time-dependent operators.

I think someone from Oracle had a presentation about their work in the same area a couple of years ago.

It allows "convenient" (though not necessary efficient) handling of queries like:

What would the data have looked like if I had queried it on 10th Feb allowing for the fact that there was an error on 9th Feb that wasn't corrected until 11th Feb - and I want to see the correct item, not the error.

-- 
Regards

Jonathan Lewis
http://jonathanlewis.wordpress.com