Re: Database design, Keys and some other things
Date: Tue, 27 Sep 2005 12:22:59 GMT
Message-ID: <DQa_e.4897$QE1.1289_at_newsread2.news.atl.earthlink.net>
"Marshall Spight" <marshall.spight_at_gmail.com> wrote in message
news:1127799407.754373.267390_at_g49g2000cwa.googlegroups.com...
> How can you derive age if birthdate isn't an attribute of the
The decomposition of the universe into entities and attributes is somewhat
subjective. (See the discussion of "nominalism" elsewhere in this thread).
The modeling of attributes is somewhat situation dependent, much as we would
like to pretend that it is not.
If I'm creating a data model for a maternity ward, I'm going to model "date
of birth" as an attribute of a birth.
> person? Where would you get the birthdate from?
The person(s) born would inherit the attribute due to their relationship to
the birth.
It's a different model for a different situation. Received on Tue Sep 27 2005 - 14:22:59 CEST