# Re: How is this collection called?

From: Paul <pbrazier_at_cosmos-uk.co.uk>
Date: 31 Mar 2004 08:35:11 -0800

Michael Mendelsohn <keine.Werbung.1300_at_michael.mendelsohn.de> wrote in message news:<406A9DE2.D88C80CC_at_michael.mendelsohn.de>...
> I thought that your "packing it in" approach was a bit unfair, counter
> to my (personal) intuition how aggregation should work.
>
> I'd define aggregation to fulfil the axioms that
>
> x is-in A => x is-in A*B
> x is-in B => x is-in A*B
>
> and that rules your approach out, because with
>
> > Define a*b as "a U {b}" (where U is set union)
>
> x is-in b => x is-in A*B breaks.

Well now you have to specify exactly what you mean by "is-in".

For sets, you have have set membership.

But if you think in terms of physical boxes, imagine a small box inside a medium box, which in turn is inside a large box. For these things you could say the small box "is-in" the large one, even though it isn't directly inside.

I think it's just the same (isomorphic to) as the tree example?

Paul. Received on Wed Mar 31 2004 - 18:35:11 CEST

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