Re: database design method

"Jan Hidders" <hidders_at_REMOVE.THIS.uia.ua.ac.be> wrote in message news:3dcfc941$1_at_news.uia.ac.be...
> >> This is of course their good right but I hope the authors realize how
much
> >> better for the acceptance of their model it would be if it were on line.
> >> Think of ODMG/OQL and W3C/XML.
> >
> >How much difference do you think it would make? I agree that their model
> >could certainly be 'marketed' with more, err pazazz.
>
> Indeed, and if the tone at dbdebunk became a bit less aggressive people
> might actually start to listen again.

You do have a point there - I might try to pass it on.

> >Are there arguments in favour of recursively defined types in the
relational
> >model? I don't recall D&D explaining why they disallow them.
>
> Trees are a very common data structure. Also think of semistructured data.
> If you don't support that then people will add their own domains to store
> them in and then they will be out of reach of the query optimizer.

True, but would your tree tuple example be the best way of implementing a tree data-structure anyway?

> >What would a valid value of Tree look like?
> >
> >{"NodeA:Value1", ("NodeB:Value2", ("", {}) )}
>
> Yeah, something like that.
>

So

     ("", {})
and therefore

    {}
would be valid values of that type? Doesn't look quite right to me.

Regards
Paul Vernon
Business Intelligence, IBM Global Services Received on Mon Nov 11 2002 - 17:53:51 CET