Re: two nasty schemata, union types and surrogate keys
Date: Mon, 21 Sep 2009 05:45:15 -0700 (PDT)
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. Whether 'an assertion that is supposed to be true' is equivalent to 'a piece of information presented as having objective reality' [fact (5) accoring to Merriam Webster] is beside the point. My point is that it is not objects that are recorded, but supposedly true statements about objects.
> As I have said before, it
> is useful to think of the content of a database as being like the
> testimony in a court case.
I don't think that's very useful at all. The content of a database isn't necessarily tagged with who said it and when they said it, but a deliberating jury knows who said what when and can therefore weigh each statement accordingly. Without a record of who said what when, it is best to suppose that what is in the database is true.
> My point being: you don't care, and we don't have to care (for the
> purpose of designing the database or the software that operates on it),
> about facts. All that matters is that we can make the inferences that
> we should be entitled to make from the assertions. Whether the
> inferences turn out to be factual or not is just not our business.
> I can't bring myself to discuss the indentity issue. I am hopelessly
> bored with the idea that every particle and every concept has a
> barcode buried in it somewhere if we look hard enough.
It is not an issue of identity but rather identifiability. If a thing can be distinguished from all other things, then it can be named. It is lucky that first-order languages sport an infinite supply of constant symbols.
> The problem of
> identity is always solved by the business process, and if it isn't,
> that's life's way of saying it doesn't need solving.
Received on Mon Sep 21 2009 - 07:45:15 CDT