Re: One-To-One Relationships

From: rpost <>
Date: Thu, 20 Dec 2007 20:40:28 +0100
Message-ID: <ad31a$476ac52c$839b4533$>

JOG wrote:

>> >> > We can only ever
>> >> >identify things from observable attributes (and refer to them by
>> >> >attributes too!).
>> >> Certainly, but we don't always make those attributes explicit.
>> >Yes we do. Always.
>> Not in my experience.
>Then do you get sent messages from an omnipotent higher being to tell
>you the identity of something! ;) I simply cannot think of any example
>of how something is identified without using explicit, identifying

Yes, you can. Suppose, one morning I feel really ill, so I pick up the phone, call our secretary and say: "Hello <name>, I'm not coming today, I'm going to have to stay in bed." As a result of this phone call, an update is issued on the employee database, to register my absence due to illness on this day. The secretary has identified me by my voice, not by anything the database registers about me.

But of course I also have to identify the tuples in the database relevant to this update. This identification must ultimately rely on externally observable information that is observably associated with me (my name, employee number, whatever). But that identification may not be direct: it can rely on the use of internal references (surrogates, oids).

I notice the discussion has progressed elsewhere so I won't continue here.

Received on Thu Dec 20 2007 - 20:40:28 CET

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