Re: Nulls, integrity, the closed world assumption and events

JOG wrote:
> David wrote:
>
> > JOG wrote:

[snip]

> > What do you think of the idea to favour direct representation of events
> > in a RDB? It is my impression that this tends to lead to normalised
> > designs that properly deal with the closed world assumption, avoid
> > nulls, ensure simple updates, and makes it easy to think about strong
> > integrity constraints.
>
> I agree with the principles of your viewpoint - but I would not call
> term it an 'event' necessarily. Codd called it a "relationship",
> although he still had to fit the concept into the relations he was
> already using in his 1969 paper. (Perhaps a better word would be
> 'observation'?) Either way a term that had no semantic link to the
> attributes of an entity would be optimal. I'd heartily recommend you
> have a look at Obejct Role Modelling (a competitor to E/R modelling),
> as it has the same philosophy that I believe you share underpinning it.

I would rather keep my viewpoint stronger (even though it becomes less general). An event is characterized by being immutable and therefore the DB tends to be pure additive. This has a number of benefits. For example updates are guaranteed to be very fast, replication and synchronisation is fast, archiving of old data is trivialized, merging of different databases is conceptually easier.

The event oriented modeling approach implies that you store a person's birth date rather than their age. Of course an experienced DB designer would do that as a matter of course, but it's nice to see an underlying principle. Received on Tue Jan 09 2007 - 02:07:04 CET