Re: database design method

Lauri Pietarinen wrote:
>
>To be spesific the closure stuff in TTM is actually
>a "Very Strong Suggestion" :
>
><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?

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