Re: Newbie question about db normalization theory: redundant keys OK?
Date: Sun, 23 Dec 2007 17:05:03 GMT
Bob Badour wrote:
> I am not sure Gray's stuff is incompatible with the information
> principle. It seems orthogonal to me.
I wouldn't argue with that but the distinction I'd prefer to think of as more useful is that concurrency theory viewed from the perspective of an rdbms operates at a physical level, often, maybe always, using artifacts such as "transaction id's, session id's" and so forth, that are hidden from apps.
My complaint about conventional concurrency theory is that (as far as I know) it has never tried to express how a purely logical view that is visible to an application can achieve the same effects as a typical concurrency or lock manager component. I think one likely reason for this is that the concurrency theorists take physical persistence as their starting point. Given that, it's not surprising they would ignore the possibility of a suitable app language using a relational algebra to prototype the same effects.
While implementing this might seem to deny one of Codd's goals, that of putting as much common logic in the rdbms rather than in app code, I also note that for the larger apps I've seen, there never failed to be some requirements compromise or other due to the concurrency strategy imposed by various dbms's.
p Received on Sun Dec 23 2007 - 18:05:03 CET