Re: Few confusing things about first normal form
Date: Thu, 23 Oct 2008 13:11:27 GMT
David BL wrote:
> Is the value of an attribute that is an RVA a scalar?
I believe it is ie., in a "containing" tuple it's a (single) relation value and (in the D&D approach) there is no way to operate on its individual tuples. Their algebra only operates on the value of the relation.
(They have an operator called UNGROUP that forms a different relation that has no RVA's. Definition in thethirdmanifesto.com, see appendix A. They don't the equality operator to treat the second relation as equal to the first even though some of the possible values for the containing /GROUPed relation might have exactly the same information as the UNGROUPed one. However, I don't believe they forbid an operator apart from equality that decides some kind of equivalence.)
Hope somebody will correct me if I've mangled what D&D say. Received on Thu Oct 23 2008 - 15:11:27 CEST