Re: Is it Possible to Enforce This Relationship at the DB Level?

On Oct 16, 7:03 am, David Portas
<REMOVE_BEFORE_REPLYING_dpor..._at_acm.org> wrote:
> On 15 Oct, 22:59, dutone <dut..._at_hotmail.com> wrote:
>
>
>
> > I'd like to enforce this based on the data model and its
> > relationships.
> > Although to me, it doesn't seem possible without an additional layer
> > of logic.
> > The need for a check assertion in a RDMS tells me that cerain
> > cituations must be enforced at a higher level. This is one of them I
> > guess.
>
> Maybe your definition of a data model differs from mine. All such
> constraints are surely part of that model irrespective of what syntax
> the DBMS uses.
>
> If you have some particular DBMS in mind then maybe someone will have
> other suggestions about features supported by that product. Perhaps a
> redesign would also be possible but I'm reluctant to begin a design-by-
> newsgroup exercise.
>
> --
> David Portas

I'm not trying to start a group design effort, but his original model certainly seems to me to have the Cell Config in the wrong place. At the logical lege, the connections should be described verbally (the cardinality can be there but blank connections between entities leaves too many unidentified assumptions.

So many business systems designers unconsciously think everything about their application is "intuitively obvious" when the truth it, it is not obvious, sometimes not even to the initiated.

  Ed Received on Fri Oct 19 2007 - 05:57:17 CEST