Re: database design method

Jan,

> >
> ><quote>
> >
> >6. D should provide some shorthand for expressing the generalized
> >transitive closure operation, including the ability to specify
> >generalized concatenate and aggregate operations.
> >
> ></quote>
>
> Strange, because in the prescriptions (thanks for the pointer, btw.) it
> already says that recursion should be allowed. Any idea why then there is
> still the need for an explicit transitive closure operation?
>

I don't necessarily have a complete answer for you but I could point out that the above "strong suggestion" talks about "providing some _shorthand_ for expressing the generalized transitive closure".

Compare it to "Strong suggestion #2:"

<quote>

2. D should include some declarative shorthand for expressing referential constraints (also known as foreign key constraints).

</quote>  

> Another thing I wondered about while reading it is if I can express the
> NEST and the UNNEST operations of the nested relational algebra. I seem to
> remember that Date & Darwen were heavily opposed to those operations, but
> the language would otherwise be certainly computationally incomplete. So,
> can I?
>
> -- Jan Hidders

Again, no expert on this but see Prescription 6 in the same link.

regards,
Lauri Pietarinen Received on Sat Nov 09 2002 - 18:20:52 CET