RE: Objective-C Object Persistency

[Vaisburd, Haim]

Andreas Höschler wrote:

> - (void)validateFreightCosts
> {
>       NSNumber *distance = [self valueForKey:@"transportorder.distance"];
>       NSNumber *rate = [self valueForKey:@"transportorder.rate"];
>       NSNumber *product = distance * rate
>       [self setFreightCosts: product];        
> }

> Now suppose that a user connects to the database and modifies the rate 
> of a transportorder. This should invalidate the property freighCosts in 
> all referenced deliveries, and this again must invalidate the value of 
> referenced stores.

We tried here to design a system that has no redundancy in the database.
That is, derived values are never stored in the database, but generated
in the object layer as the integral part of a query process.

Tima.