Re: A numerical methods viewpoint on OO/FP/Relational

"Mikito Harakiri" <nospam_at_newsranger.com> wrote in message news:SD717.8804$Kf3.99960_at_www.newsranger.com...
> In article <3b44a4a2$1_at_tobjects.newsource.com>, peter_douglass says...
> >
> >> Relational model:
 

> >> The relational model is declarative. It defines the variables
> >> and defines the constraints that the variables must satisfy.
> >> It doesn't say how these constraints must be satisfied.
> >> It simply accepts or rejects values for the variables depending
> >> on whether these values satisfy the constraints or not.
 

> >> Note, however, that the relational model also has a
> >> provision for explicitly defining dependent variables as
> >> functions of other variables.
>
> This definition is too broad for Relational, you essentially describe
 Constraint
> Databases. Relational narrows it's scope to very simplistic (and highly
> successful, as well:-) kinds of predicates.

Can you explain this? What is the "break-point" between relational databases and constraint databases? I always thought constraint databases would deal with declarative or cyclical constraints, while relational would deal with dependents as a function of independents, possibly nested.

(I'm not trying to be lazy here. I have read much of the literature, but your point never showed up on my radar screen. Perhaps a case of "what you know that ain't so" so you never look closely.) Received on Sat Jul 07 2001 - 08:26:02 CEST