Re: The original version

On Aug 6, 12:06 pm, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
> vldm10 wrote:
> > On Aug 5, 2:41 am, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
>
> >>vldm10 wrote:
>
> >>>The authors of Anchor Modeling state that their model is based on the
> >>>Sixth Normal Form. However, 6NF cannot secure binary structures. Let
> >>>us consider a relation with five attributes that are mutually
> >>>independent. This relation is in 6NF , thus it cannot be further
> >>>decomposed. If we wish to get the history for each of its attributes,
> >>>things become very complicated.
>
> >>Huh? Do you know what 6NF is?
>
> > I guess I know?
> > Do you know what 6NF is?
>
> > 6NF is defined by the authors of the “Anchor Modeling” as follows:
> > A table is in 6NF iff it satisfies no nontrivial join dependencies at
> > all.
> > (http://www.anchormodeling.com/tiedostot/6nf.pdf)
>
> > Maybe you can explain your thinking by using this definition?
>
> How does a relation with 5 mutually independent attributes meet the
> definition of 6NF?- Hide quoted text -
>
> - Show quoted text -

When I speak about an entity then in my db design I have the following constructions:
1. the concept of the entity with ( for example) 5 “mutually independent attributes”
2. the corresponding binary concepts (they are the entity attributes) 3. the corresponding unary concepts (they are the kind of) That is all what we need.

I don’t need a decomposition of the entity on 3+2 attributes, for example. I don’t know what these components represent. I don’t need 6NF. I need binary structures and they are reason why I mentioned “mutually independent attributes”.

So your note is OK, it is possible that the relation with 5 mutually independent attributes be nonloss-decomposed as non-trivial join. But it is a random, it is not a rule. With mutually independent attribute the probability for decomposition is really small. On the other hand relation can have 10 or more mutually independent attributes.

There is one other thing here, which is more important, which is badly done in the "Anchor Modeling. This is about how to do the transition from E / R model in the relational model and vice versa. I think it is necessary to define the mapping from E / R to RM, then the inverse mapping for the given mapping and in the end it is necessary to define the composition mapping. In my model I have at the outset, the binary concepts. Each binary structure has its own unique identifier of the state. Therefore, each tuple or a binary concept is uniquely defined. In "Anchor Modeling" They start from the E / R and go in the RM, so do 6NF, and return to the E / R. But it was not discussed in the paper, so it's not clear how to do it. For example the definition of 6NF is interesting:
(A table is in 6NF iff it satisfies no nontrivial join dependencies at all.)
We can note that mapping of schemas between two db models can be complex, for examples it can include constrains.

Vladimir Odrljin Received on Fri Aug 06 2010 - 18:53:34 CEST