Re: Table design question
Date: Thu, 5 Feb 2004 23:35:28 GMT
Message-ID: <HsMxJ7.Apr_at_news.boeing.com>
Bob,
Thanks for the clarification. I agree, now that I understand. Value vs. variable.
- Dan
"Bob Badour" <bbadour_at_golden.net> wrote in message
news:cpOdne8wFNQ1Wb_dRVn-sw_at_golden.net...
> "D Guntermann" <guntermann_at_hotmail.com> wrote in message
> news:HsMHuG.EtL_at_news.boeing.com...
> >
> > "Bob Badour" <bbadour_at_golden.net> wrote in message
> > news:iqmdnQhOysUkBYfdRVn-jg_at_golden.net...
> > > "Mike Sherrill" <MSherrillnonono_at_compuserve.com> wrote in message
> > > news:qimk1018kh3htkap6gkdif05j1q8705v6v_at_4ax.com...
> > > > On 25 Jan 2004 03:39:33 -0800, andrewst_at_onetel.net.uk (Tony) wrote:
> > > >
> > > > >But it isn't a domain: the domain of user ID numbers would be
> > > > >something like "any 6 digit number between 100000 and 999999" or "a
> > > > >string of between 3 and 30 letters and numbers"; whereas this table
> > > > >represents the list of users who actually exist,
> > > >
> > > > Try thinking about it this way . . .
> > > >
> > > > At the conceptual level, a domain is just a data type, and a type
is,
> > > > among other things, a set of all possible values. One way to handle
a
> > > > set of values is to store them in a table.
> > >
> > > It's the "among other things" that kills you. A variable is not a time
> > > invariant set of values and their associated operations.
> > >
> > >
> > I'm not sure I understand, Bob.
> >
> > A variable holds a single value drawn from some domain. By virtue of
the
> > fact that the domain has been defined at some point in time as a set of
> all
> > possible values with operators, it should be time-invariant as long as
the
> > type specification holds.
>
> The domain is defined for all time even if not specifically or completely
> declared to a dbms at any particular time.
> >
> > Why wouldn't it be invariant?
>
> The variable or the domain? The domain is time invariant. The variable is
> not. Nor does the variable declare any operations.
> >
> > Computing devices are constricted to rather finite sets of
> representations,
> > as is logic. Are you saying that this constraint actually does not
exist?
>
> Not at all.
>
> Received on Fri Feb 06 2004 - 00:35:28 CET