Re: Stupid Database Tricks

On Jun 14, 10:23 am, Jan Hidders <hidd..._at_gmail.com> wrote:
> On 14 jun, 12:55, vldm10 <vld..._at_yahoo.com> wrote:
>
>
>
> > Here I believe that you misunderstand what is key. I have
> > 1. the identifier of the state of an entity or relationship
> > 2. the identifier of the entity or relationship.
> > I will use shortcut IdSt for first and IdEt for second
> > Usually key is IdSt. But IdSt always goes in pair with IdEt.
> > These two identifiers have strong semantic and conceptual base.

I have a impression that our discussion start to be circular. I started it with suggestion that first we can analyze my two identifiers, you answered with a suspicion about reinventing ORM. I checked ORM and found for example that ORM don't talk about attributes. I talk pretty about the attributes. Then you switched to critic of my normal form (which I named: Simple Form). I answered on some your points; you switched focus to two identifiers. Let's try to focus on every important thing, one by one. I appreciate your comments, as I told you here - there are knowledgeable and right.
>
> Could be, but they also might be complete nonsense. For the moment it
> is absolutely unclear to me what you mean by these terms. So how about
> you giving some proper definition and/or explanation of what they
> mean?

The names of these identifiers are with exact meaning. This is reason why the names are so long.
You can find it on my website, where I presented this model. So theoretical background you can find there (No needs to write it twice). All terms are very precisely defined or I gave their construction.

> Let's, for simplicity, restrict ourselves to entities for the moment.
> I understand what it means if entities have certain attributes which
> have certain values. The state of an entity is usually defined as the
> total description of its attributes, i.e., a function that maps
> certain attribute names to their values.

As far as know this mapping defined P. Chen. This is definition of an attribute, it is not definition of the state of an entity.

>Such a state does not have an
> identifier, or even need one, since it identifies itself. So that
> raises the following questions:
> - How do you define the state of an entity?
> - How do you define the identifier of the state of an entity?
> Ideally these definitions should be in terms of entities and their
> attributes. If you are going need other concepts then please define
> and explain them properly first.
>
> The notion of identifier of an entity (in a certain entity set) is
> usually defined as a set of attribute names such that at no point in
> time there can be two entities in the entity set for which the values
> of the attributes in this set is the same. Are you using that
> defintion, or another one? If so, please define and explain it, also
> ideally in terms of entities and their attributes.
>
> Let's restrict the discussion to this for the moment. Once this is
> cleared up there is the chance of proceeding in a meaningful way.
>
> -- Jan Hidders

I want to emphasize one important thing. When I speak about DB Solution in my model (on my website or in this discussion) I always think that the solution is in form of "totally decomposed" or more precisely DB solution is set of the binary relations in the form: simple key + one attribute. I named this form: Simple Form. Here, I believe some misunderstandings can be caused by different view of DB solution.
I also didn't think to make new DB model, rather some new constructions and principles. That is why I put model in quotes, but I will use just model, without quotes - to simplify writing.

Vladimir Odrljin Received on Fri Jun 15 2007 - 21:42:56 CEST