Re: Principle of Orthogonal Design

On Jan 9, 12:49 pm, DM Unseen <dm.uns..._at_gmail.com> wrote:
> On 9 jan, 02:51, JOG <j..._at_cs.nott.ac.uk> wrote:
>
>
>
> > I was wondering what your current stances towards the principle of
> > current design is cdt - info about the POOD is actually pretty sparse
> > on google, which has not helped my own understanding. I gather that
> > Date has realigned his opinion - although what to I know not - and
> > that Darwen rejected the original POOD paper outright given that
> > McGovern posits that:
>
> > R1 { X INTEGER, Y INTEGER }
> > R2 { A INTEGER, B INTEGER }
>
> > violates the principle, whatever the relations' attribute names.
> > Instinctively it does seem rather odd that a predicates such as:
>
> > * on Day:X the shop had noCustomers:Y
> > * on Roll:A, the dice showed the Number:B
>
> > cannot share the same database. Have I interpreted the debate
> > correctly? Any insights or corrections are, as ever, appreciated -
> > POOD is certainly thought provoking, and the concept that an update
> > need not require specifcation of a table name is an interesting one.
>
> My understanding is that the debate centers around typing.
>
> Date advocates strong typing: ie X is of type "shop number" and A is a
> "roll number", both represent different aspects of the UOD so they
> have a different type (I disregard subtyping here for simplicity),
> *even if* the actual underlying representations (e.g. natural numbers)
> would be the same. Having different types, means the type engine can
> distinguish them.

Hmmm, I see. I have always viewed a type as a set of values and a collection of allowable operations. If there exist two data types where these values and operations are the same, well as far as I can logically see, that makes them the same thing (even if they have two references).

Now I could follow the concept more if Date & McGovern weren't conflating the concept of attribute and type, and defined an attribute as a (role-name, type) pair, but as it stands is seems very odd to me.

>
> DM Unseen
Received on Thu Jan 10 2008 - 02:31:26 CET