Re: MV counterexample

In message <40a11362$1_at_post.usenet.com>, x <x-false_at_yahoo.com> writes
>> If we want to have user-defined datatypes like "age" or "sex", the user
>> is going to have to be able to program (in some sense or other) the
>> integrity checks, therefore integrity checking must be a user-space
>> phenomenon. I just don't see how you can get round it. By definition,
>> the database itself cannot use data to do primary integrity checks - it
>> needs metadata. But the user can't provide metadata because the database
>> itself has no way of understanding it - it'll think it's data. Catch 22.
>
>Well, in the DKNF there are only two checks :
>- domain membership
>- keys enforcement

What's DKNF? :-)

>One of the problems the relational model is supposed to solve is :
>"In contrast, the problems treated here are those of data independence--the
>independence of application programs and terminal activities from: GROWTH in
>data types"
>:-)

What does that mean? Seeing as I was responding to people who said that "you need user-defined primary data types to have a proper relational database", it sounds like you're saying the whole point of a relational database is to *restrict* datatypes in order to get a manageable system :-)

Cheers,
Wol

-- 
Anthony W. Youngman - wol at thewolery dot demon dot co dot uk
HEX wondered how much he should tell the Wizards. He felt it would not be a
good idea to burden them with too much input. Hex always thought of his reports
as Lies-to-People.
The Science of Discworld : (c) Terry Pratchett 1999