Re: 1NF (Marshall)

paul c wrote:

> I would say SU doesn't mean the same thing as S. Maybe this isn't a
> problem to anybody else, but it troubles me if you are saying that the
> meaning can be preserved by unnesting alone, eg., without the
> introduction of other attribures than P#.

 I agree.

 In the first place, the "unnesting" here loses information; specifically, how many of each part was shipped. That might be OK for the purposes of defining the operation but I observe that it will significantly complicate data modeling.

 In the second place, it's entirely reasonable to define a model which organizes the same information and doesn't require the same kind of mixing of sets and types.

 I'm a fan of the simple, old-fashioned definition of 1NF. Each attribute of a tuple has exactly 1 element value from a domain. Received on Sun Jan 21 2007 - 04:35:57 CET