Re: 1 NF
Date: 28 Feb 2007 12:56:37 -0800
On 28 fév, 21:02, "-CELKO-" <jcelko..._at_earthlink.net> wrote:
> >> I read an interview with Chris Date (http://www.dbmsmag.com/int9410.html) which made me a little bit confused. He claims that having an array as a column values doesn't violates 1NF. Is this the common opinion at comp.databases.theory too? <<
There are precise definitions to 1NF. DATE is indeed a knowledgeable source of information when it comes to RM deifnitions...Just ignore CELKO"S BS and you will be fine...
IGNORE CELKO's DEFINITION he has no clue about RM!!! (but pretends to)
> Pretty much, if you can ser up the rules for arrays so that they form
> a Domain, in a relational sense. I would need to have rules for
> manipulating them, but most important I need Theta Opertors which can
> be used to define JOINs with columns in those domains.
> There is also a difference berween "atomic" and "scalar" in the
> definition of 1NF. For example (longitude, latitude) is atomic (Greek
> for "without parts" or indivisible) because it resolves to one point
> in space. But longitude and latitude are scalar values by
> themeselves (I can go into scales and measurements, but the idea is a
> set of discrete values, a way to assign a value to an event, blah,
Listen to that crappola...CELKO is indeed an ignorant.
Atomic and scalar are only minor prerequisites for a logical design to be 1NF. If you can not validate that logical entities are relations (each tuple is a TRUTH validated proposition) then it is not 1NF.
> >> Does a blob containing an image violates 1NF? <<
1 NF is a logical concept. A blob is a physical implementation. The question should have been at the first place: may the implementation of BLOB be *possibly* represent the logical design in 1 NF. The answer is NOT A CHANCE as BLOBS break the primary requirement of independence between logical and physical layer and the fact that a BLOB attribute included in any proposition can not make a relation out of it (1NF dictates that all information MUST be stored as relations)
> There is hard! Can you break it down into meaning parts -- i.e. is
> the blob atomic? That one is hard, since pictures have semantic
> content -- "Look!! There is Lindsay Lohan behind a tree!" but it is
> really hard to use theta operators because semantics lead to fuzzy
> logic. So I would say that the fuzzy logic would override the usual
> 3VL for RDBMS and we do not have a proper domain.
Confusing explanations...Just ignore them... Received on Wed Feb 28 2007 - 21:56:37 CET