Re: candidate keys in abstract parent relations

"paul c" <toledobythesea_at_oohay.ac> wrote

> Putting words in your mouth, can't resist, sorry. To amplify, I would
> say a person can't have a key even though a relation about persons could.

Excellent!

You've given me more food for thought about "entity and identity". Thanks!

> Safeway here charges 50% more, no exaggeration if you aren't a 'member'.
> Need to give your telephone number. They won't accept mine because I
> share it with friend who has already given it to them. Since friend is
> female and I'm not, I can't fool them. On the other hand they can't
> fool me, which is why I don't shop there.
>

What, you mean that heteros can't share telephones? Sounds like "Men are from Mars, Women are from Venus" all over again.

>
> Sometimes I think modellers go too far trying to ascribe dbms attributes
> to the natural world. Certainly big biz and governments do.
>

Information is about something. If not, who cares?

>
> I do agree with whoever posted to the effect that it's good to avoid
> showing internal or 'artificial' keys even though it's sometimes
> necessary to subsequent transactions, some of the more common examples
> being social security numbers and postal codes.
>
Or bank account numbers, or credit card numbers, ...or your telephone number.

BTW, your telephone number, if it's a land line, doesn't identify your telephone. It identifies the line your telephone is plugged into. There is more to this than meets the eye. Received on Sat Jan 21 2006 - 12:39:37 CET