Re: two nasty schemata, union types and surrogate keys
Date: Mon, 21 Sep 2009 15:19:29 -0500
> On Sep 21, 10:27 am, Roy Hann <specia..._at_processed.almost.meat> wrote:
>> Brian wrote:
>> > On Sep 21, 3:41 am, Roy Hann <specia..._at_processed.almost.meat> wrote:
>> >> Brian wrote:
>> >> > Databases don't record objects: they record facts [...].
>> >> Admirably close, but not quite cigar-worthy. Databases record
>> >> *assertions* of fact. The assertsions may be sincere and truthful, or
>> >> sincere but false, or deceitful and false.
>> > Whatever. What is in the database is supposed to be true.
>> Says who?
> Everyone who advocates the closed world assumption.
The closed world assumption doesn't tell you anything about what is actually in the database; it tells you how you are entitled to manipulate what you find in the database. I hinted at that in my first post when I wrote "All that matters is that we can make the inferences that we should be entitled to make from the assertions."
>> It doesn't need to be true, and it can't be guaranteed to be
>> true, so it is wise to remember that what's in the database is just
>> claims and assertions. It is completely sufficient that the database is
> I don't think that it is sufficient.
Well that's too bad, 'cos that's all you can have.
-- RoyReceived on Mon Sep 21 2009 - 15:19:29 CDT