# Re: An inconsistency or not?

From: Denny Vrandecic <dvr@aifb.uni-karlsruhe.de>
Date: Fri, 01 Apr 2005 14:08:10 +0200
Message-ID: <424D39AA.8040005@aifb.uni-karlsruhe.de>
To: Chris Purcell <cjp39@cam.ac.uk>

```

Chris Purcell wrote:
>
>> That's wrong.
>> A owl:intersectionOf [B, C, D].
>> A owl:equivalentClass B.
>>
>> can be simplified to
>>
>> B owl:intersectionOf [C, D].
>> A owl:equivalentClass B.
>
>
> Unfortunately, this is not true:

Actually, fortunately. :)
Dumb error of mine. Kids having set algebra wouldn't have made it, and
now I feel very dumb. Thanks for the correction!

My mistake was that with A=B and A = B /\ C /\ D I substituted A with B
in the second formula, thus making B = B /\ C /\ D , which I thought
would simplify to B = C /\ D, which is not true, but rather B <= C /\ D
(with /\ being intersectionOf and <= subClassOf).

> A = B = { x }; C = D = { x, y }
>
> intersect(B,C,D) = { x } = A
> but intersect(C,D) = { x, y } != B
>
> Chris
>
>

Thanks, denny
```
Received on Friday, 1 April 2005 12:08:14 UTC

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