Re: The Theoretical Foundations of the Relational Model

In message <3d1666c3.35718780_at_news.verizon.net>, JRStern <JXSternChangeX2R_at_gte.net> writes

>
>There's a big debate these days on just what a primary key is for. In
>olden days, it was supposed to be the unique specifier for the
>real-world object, which again assumes there is such a thing, say
>"Smith, Jane". Disregarding the problems of there being lots of
>"Smith, Jane" there is the question of what happens when she gets
>married and (in cases where it still occurs) changes her name.
>Cascading updates, to be sure, but there are places that does not do
>the trick.

There isn't any conflict here. It's difficult to find a natural key in a lot of cases, I've suggested a suitable one for people. It's made up of the latitude, longitude, altitude and time of their birth. It's not very practical but it is a valid key.

>
>Hence, these days, a lot of practitioners, whatever the merit of the
>thing, use a synthetic primary key for every table. This is sort of a
>half-assed attempt to introduce identity into the relational model,
>where you would say it does not need to be, or was already present.

I'd say it's an attempt to remove identity from the implementation, it already exists in the relational model.

>The situation is entirely muddled.

True.

-- 
Bernard Peek
bap_at_shrdlu.com

In search of cognoscenti