Re: Can we solve this -- NFNF and non-1NF at Loggerheads

"Paul" <paul_at_test.com> wrote in message news:42076e88$0$42537$ed2619ec_at_ptn-nntp-reader03.plus.net...
> Roy Hann wrote:
> > 1NF does not "mean values are simple or indivisible". It just says that
for
> > the purpose of the relational theory, the divisibility (or internal
> > structure) of values of a given type is of no interest or use within the
> > theory. The theory does not make use nor reference to the internal
> > structure of a value of any type. The theory therefore does not need to
> > define what atomic means. The term "atomic" is a just a narrative
> > short-hand that Codd used to say, "That's stuff I don't care about, so
> > forget about it from now on as you read this paper." I can't think of
any
> > other theory where a precise definition is demanded for things that are
> > *intended* not to be discussed. Plane geometry isn't required to define
> > colour for the purpose of excluding it from discussion.
> >
> > There is nothing in RT that *prevents* values from being divisible,
there
> > never was, and it would plainly be stupid to want it that way.
>
> This sounds to me like an excellent summary of what "1NF" and "atomic"
> means. I can't believe we go round in circles discussing this point when
> it really is this simple!
>
> Paul.

Okay, I will cite a well respected source supporting my position, then you do the same. From "Fundamentals of Database Systems, Third Edition", Elmasri/Navathe, pages 485-487 Addison-Wesley, 2000:

"First normal form (1NF) is now considered to be part of the formal definition of a relation in the basic (flat) relational model (Footnote 11: This condition is removed in the nested relational model and in object-relational systems (ORDBMSs), both of which allow unnormalized relations.); historically, it was defined to disallow multivalued attributes, composite attributes, and their combinations. It states that the domain of an attribute must include only atomic (simple, indivisible) values and that the value of any attribute in a tuple must be a single value from the domain of that attribute. Hence, 1NF disallows having a set of values, a tuple of values, or a combination of both as an attribute value for a single tuple. In other words, 1NF disallows "relations within relations" or "relations as attributes of tuples." The only attribute values permitted by 1NF are single atomic (or indivisible) values. ... The first normal form also disallows multivalued attributes that are themselves composite. These are called nested relations because each tuple can have a relation within it..."

Your _opinion_ is not solicited. Cite some facts from a published source. Received on Mon Feb 07 2005 - 16:49:09 CET