Re: FK - automatic value change when parent changes
Date: Sun, 28 Feb 2010 17:57:00 -0800 (PST)
On Feb 27, 12:51 am, "Jonathan Lewis" <jonat..._at_jlcomp.demon.co.uk> wrote:
> "joel garry" <joel-ga..._at_home.com> wrote in message
> > 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 time-
> dependency and time-dependent operators.
Hardly call 2006 "classic." :-)
> 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.
Yes, this is the type of thing I'm referring to, though it far too often reflects a more basic change in data definitions. I haven't yet seen 6nf used in any way except as a custom written fix on the fairly straightforward types of systems I work on, and only implicitly. MRP's and ERP's take years to develop, and more years to life cycle in production. And the time series stuff I've written to plop into those started before 2006.
It's good that someone big has made a theoretical basis for this, but then again, kids today seem to think dinosaurs R us.
-- _at_home.com is bogus. http://boards.straightdope.com/sdmb/showthread.php?t=553635Received on Sun Feb 28 2010 - 19:57:00 CST