Re: Is it Possible to Enforce This Relationship at the DB Level?
Date: 19 Oct 2007 11:34:08 -0700
On Oct 18, 8:57 pm, Ed Prochak <edproc..._at_gmail.com> wrote:
> 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.
Wrong place, how so? The diagram got screwed up so let me clarify.
The CLIENT can provides a SERVICE
Each SERVICE is described by a SPREADSHEET
The SPREADSHEET must conform to a SPEC
A SPEC mandates that one supply values for its FIELDS
A SPREADSHEET has many CELLS which correspond to to FIELDS of its chose SPEC Received on Fri Oct 19 2007 - 20:34:08 CEST