Re: Covering Axiom Question

Hi Toby

Just read your answer when sending mine. Good news is that we agree :)
Not sure, though, how it's linked to the open world assumption. Clearly, in
an open world, another triple might provide tomorrow the information that
:Bob is actually a Monkey (in your vastly simplified biology).
But you can also live in the closed world of your current triple store with
the fact that :Bob is either a Human or a Monkey, never decide which, and
nevertheless derive facts like :Bob is a Mammal, has a birthdate, whatever.

Bernard

2009/10/2 Toby Inkster <tai@g5n.co.uk>

> On Thu, 2009-10-01 at 19:16 -0400, Kevin Tyson wrote:
> > What I don't understand is why an instance of the covered class does
> > not create an inconsistency.
>
> It's a consequence of the open world assumption.
>
> If I define:
>
>        :Primate owl:equivalentClass [
>                owl:unionOf (:Human :Monkey)
>                ] .
>        :Human owl:disjointFrom :Monkey .
>
> (And I realise I'm vastly oversimplifying the biology here!) then a
> statement like this:
>
>        :Bob rdf:type :Primate .
>
> is not inconsistent. In the first snippet, you've asserted that all
> primates must be human or monkey, and cannot be both. In the second,
> you've asserted that Bob is a primate. Therefore, Bob must be human or a
> monkey, but not both.
>
> But because of the open world assumption, that's OK. Bob *is* either a
> human or a monkey, and not both - but we haven't said which he is.
>
> --
> Toby A Inkster
> <mailto:mail@tobyinkster.co.uk>
> <http://tobyinkster.co.uk>
>
>


-- 
Bernard Vatant
Senior Consultant
Vocabulary & Data Engineering
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