Re: RM's Canonical database

AndrewMackDonna wrote:
> Marshall wrote:
> > Ron Jeffries wrote:
> >
> >> In favor of putting a common rule in the DBMS is that it is centralized. The
> >> "Once and Only Once", or "DRY" principle suggests that it should be there.
> >>
> >> Another possibility for a location for such a rule is in a middle tier, where it
> >> can also meet the DRY principle.
> >
> > But then you lose the centralization.
>
> Not necessarily, its moved thats all. There is still only one instance
> of it in the company.

(Some clarification: I am assuming Ron is talking about the idea of having an application server "in front of" the dbms that implements business rules via whatever language the app server code uses; e.g. Java.)

What you say would only be true if there was no update access to the dbms except through the app server. In practice, this is rarely the case; the larger the enterprise, the less likely this is to be true. Furthermore this approach introduces friction in the development process, because the app server interface is in practice always less flexible than a generic SQL interface, and every additional application requirement must be hand coded into the app server.

In other words, this approach doesn't scale.

Marshall Received on Mon Jul 03 2006 - 14:14:23 CDT