Re: object algebra
Date: 24 Feb 2004 13:25:13 -0800
Message-ID: <4b45d3ad.0402241325.6eb056d5_at_posting.google.com>
> And the model says no nulls, or at minimum says nothing about them.
If the RDM model does not address NULLs, it is incomplete. Or there are de facto rules governing NULL otherwise vendors could implement NULL handling differently causing problems. If you were to code a RDM database, you would have to address NULLs. Or do you think otherwise?
> Codd was, with all due respect, wrong about the utility of nulls.
Codd is correct about the utility of NULLs with respect to RDM because it creates them. If you create something, you are responsible for it by default.
> They violate relational closure in many ways,
> so that would tend to imply they're not allowed.
NULLs do violate relational closure and should not be allowed. Because RDM is (slightly) flawed, using it to represent some kinds of things results in NULLs. But not with TDM. Received on Tue Feb 24 2004 - 22:25:13 CET