Re: Counting propositions
Date: Thu, 17 Jun 2004 17:40:04 +0300
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"Tony" <andrewst_at_onetel.net.uk> wrote in message
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> > > > > > > > > > Ok. But why there is a need to know this number ?
> > > > > > > > > > It is like saying "today I made 100 affirmations".
> > > > > > > > >
> > > > > > > > > Have you never wanted to know how many of something you
had?
> > Can
> > you
> > > > > > > > > not envisage a large business wanting to know, for
example,
> > how
> > many
> > > > > > > > > employees it has?
> > > > > > > >
> > > > > > > > Employees yes. Propositions no.
> > > > > > >
> > > > > > > Very droll ;-)
> > > > > > >
> > > > > > > But the fact is that from the N propositions we have that say
"We
> > have
> > > > > > > an employee named xxx with salary yyy ...", we can deduce the
> > useful
> > > > > > > fact that we have N employees - simply by counting the
> > propositions.
> > > > > >
> > > > > > What made you so sure.
> > > > >
> > > > > What makes you so unsure? Are you making some kind of
philosophical
> > > > > point that I'm not getting?
> > > >
> > > > Well, because you don't directly count employees, but you count
> > propositions
> > > > about employees instead, it is a legitimate question to ask if the
> > result is
> > > > accurate and why.
> > > >
> > > > Other reasons:
> > > > - the database may contain propositions about past, current and
future
> > > > employees
> > > > - the database may contain propositions about employees in different
> > > > relations (or relvars)
> > > > - it might be hard to distinguish propositions about employees from
> > other
> > > > propositons in the database
> > >
> > > Well, you ceertainly have to know what the propositions mean before
> > > you can get a meaningful answer by counting them. If the propositions
> > > include past and future employees then you should ensure that you only
> > > count the propositions about current employees by adding the
> > > appropriate WHERE clause.
> > >
> > > It shouldn't be at all hard to distinguish propositions about
> > > employess from other propositions in the database, because a
> > > relation/table must only hold propositions of one type.
> >
> > So you say that the employees are in *one-to-one correspondence* with
the
> > propositions about employees, or something like that and this is the
reason
> > you can count propositions to determine the number of employees ?
> I do, though I sense I may be walking into a trap ...
:-)
> I guess the term "external predicate" comes in here, i.e. the > knowledge that these propositions EACH ??? assert the employment of 1 > employee is implicit.
You see, there are propositions that assert the employment and propositions that assert other things about the employee.
> From that, one can deduce that the existence of > N propositions implies the existence of N employees.
Not true. There might be more propositions per employee (without duplicates).
> Whether these > "propositions" are stored in a DBMS or written down in biro in a > spiral-bound notebook, it is obvious that one can count the (known) > employees by counting the number of entries (provided we disallow > duplicates).
Define duplicates :-)
So the correspondence isn't one-to-one.
You have to work to get a one-to-one correspondence.
Why do you insist in counting the propositions, for counting the employees
then ?
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