Re: Nulls, integrity, the closed world assumption and events

David wrote:
> Brian Tkatch wrote:
> > Cimode wrote:
> > > David wrote:
> > > > Consider the following relation
> > > >
> > > > person(P,M,F) :- person P has mother M, father F.
> > > >
> > > > By induction a non-empty
> > > > database would have to be infinite.
> > > A false premise makes all deductions coming from it false. Closed
> > > World Assumption does not say anything about the number of element that
> > > belong to a domain of values from which one attribute values are
> > > derived. In the case of a *person* domain, the number of elements in
> > > the set is certainly finite. Therefore, the number of propositions
> > > involving person as an attribute is limited as well.
> >
> > Would not the question be better stated:
> >
> > If a table lists linked chains (with the linked-to link), how is the
> > final link (whether first or last) stated?
> >
> > In such a case i link the item to itself.
>
> You suggest a proposition stating that a person is their own
> mother/father?

Yes.

In a cause-effect table that records all causes and effects has to assume a circular relationship for either the prime cause or (current) final effect.

If the table in question here was to denote parents and their children, there would be allowance for an entry of no children, thus ending the chain. However, the case here is people and their parents, without the option of no parent.

This means the chain must be circular, the question is to which link. Being it would create an impossible relationship for a parent to have a child as his parent, the circular relationship must be to itself.

So yes, i would indeed suggest a proposition stating that a person is their own parent.

B. Received on Wed Jan 10 2007 - 17:04:51 CET