Re: MV Keys (was: Key attributes with list values)

Marshall Spight wrote:
> David Cressey wrote:
> > "mAsterdam" <mAsterdam_at_vrijdag.org> wrote
> >
> > > If I change the order of the items in the list,
> > > does that make it a new key? I would think so. (See below)
> >
> > In other words, an onion and mushroom pizza is different from a mushroom and
> > onion pizza.
> >
> > Here we go again.
>
> Ha ha!
>
> I've always maintained that any question about whether a collection
> is ordered or not (such as a collection of pizza toppings) is a
> question of domain modelling. The question of whether
> onion, mushroom = mushroom, onion is exactly the question
> of whether this particular collection is considered ordered
> in this particular domain. To answer that, we need a
> domain expert.
>
>
> Marshall

Yes! This point is crucial and why (dawn ;) one should desperately avoid the conceptual squashing of sets, multisets, orderings, peruvian monkey fish, etc., into a single catchall "list" construct.

It isn't just about the pros and cons of passing cognitive load onto the user, its about allowing the system to be capable of maintaining integrity and making formally correct decisions. As far as I can see, the domain expert that Marshall specifies above can and *should be* the system itself, as defined to it at design time when the domain was specified. Received on Mon Feb 27 2006 - 04:13:33 CET