Re: two nasty schemata, union types and surrogate keys
Date: Thu, 24 Sep 2009 11:42:19 -0700 (PDT)
Message-ID: <5dd7bd1f-183f-4733-8aab-cf0e45fa62ba_at_l31g2000vbp.googlegroups.com>
On Sep 22, 10:13 am, Brian <br..._at_selzer-software.com> wrote:
> ... But if I don't suppose that what is in the database is
> true, then there's no point in even having a database. ...
And here you make a hideously common mistake, one that seems to be more common to governments for some reason, but happens in the private sector too.
The contents of a database are assertions of fact made by the
providers
of said information. If you are running (say) an order entry
database, it's
reasonably safe to assume that the assertions in the database are
true.
Even then, errors in data entry (for whatever reason) may lead to
database assertions that don't match the "real world" (i.e. are
false.)
If the data arrives via entities who either don't care or are actively
hostile to your goal in collecting data, your database is liable to be
full of assertions that don't match reality. That doesn't make it
not-a-database, nor does it necessarily invalidate the notion of
collecting the (untruthful) data. It DOES mean that you must treat
the database as WHAT IT IS -- assertions of fact, NOT fact.
Karl Received on Thu Sep 24 2009 - 20:42:19 CEST