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Re: No exceptions?

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Sat, 01 Jul 2006 23:05:41 GMT
Message-ID: <9dDpg.4806$pu3.112227@ursa-nb00s0.nbnet.nb.ca>


Rich Ryan wrote:

> "Bob Badour" <bbadour_at_pei.sympatico.ca> wrote in message
> news:MTzpg.4709$pu3.109666_at_ursa-nb00s0.nbnet.nb.ca...
>

>>Jon Heggland wrote:
>>
>>>Bob Badour wrote:
>>>
>>>>Jon Heggland wrote:
>>>>
>>>>>"Every attribute" would also be a superkey (speaking loosely). The

>
> empty
>
>>>>>set is a subset of every set.
>>>>
>>>>I respectfully suggest the confusion caused by your use of key without
>>>>the 'candidate' qualification demonstrates exactly why we have the term.
>>>>I suppose irreducible key would do just as well, but for historical
>>>>reasons, candidate key already means an irreducible key.
>>>
>>>I don't think the confusion is on my part. "Key" (as opposed to
>>>"superkey") already implies irreducibility; that's the point of the
>>>superkey/key distinction. A "candidate key" is certainly irreducible
>>>(due to being a key), but "irreducible key" is redundant.
>>
>>Candidate key, superkey and proper superkey all have different precise
>>meanings and all of them are keys.
>>
>>A definition is like a contract for communication and understanding.

>
> Well done. However, I would slighlty edit: A definition IS A contract for
> communication.
>
>
>>When you arbitrarily redefine key to mean candidate key, you breech that
>>contract and the result of that breech is confusion.

>
> Do you really mean "breech" or did you mean "breach" ?

Breach, of course. Received on Sat Jul 01 2006 - 18:05:41 CDT

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