what data models cant do

"Kenneth Downs" <knode.wants.this_at_see.sigblock> wrote elsewhere:

> IMHO the unified theory describes data organized into tables but which
> contains system-managed columns and tables. Because all business rules
> resolve to database specifications, we are not so much seeking a model
> that
> allows management of human-created code, but rather a model that fully
> supports the generation of automated values. The normal toy example is an
> automated column extended = price * qty, but if you systematize that and
> add some other nifty stuff, you can create a database that can do anything
> that procedural code can do, and organize the entire process flawlessly
> from analysis to real-world use.

I have been looking around for an article in which I had seen a similar treatment of "derivations" since you posted the above, and this evening found it again. You may already have seen this one:

What data models cant do --- David Hay
http://www.essentialstrategies.com/publications/businessrules/brules.htm

In summary, the article details at least four categories of things not adequately described in data models:

1. implied assumptions
2. when optional relationships are activated
3. how to keep multiple paths between entities
4. derivations [derived data --- see above]

Pete Brown
Falls Creek
Oz
www.mountainman.com.au Received on Sat May 14 2005 - 10:33:08 CDT