Re: some information about anchor modeling

From: Eric <eric_at_deptj.eu>
Date: Mon, 5 Nov 2012 21:44:14 +0000
Message-ID: <slrnk9gcpe.8dj.eric_at_teckel.deptj.eu>



On 2012-11-04, vldm10 <vldm10_at_yahoo.com> wrote: ...
>> Google gives a Safari book preview of a few lines, below. (I have the
>> book, this enough to give you an idea of his usage, introduced here.) See
>> http://en.wikipedia.org/wiki/Relational_Model/Tasmania re kernel entities
>> of RM/T.

> Let me comment only few basic things from this web site. In the section
> "Summary of RM/T", the following basic concepts are defined:

(re-ordered)

> (ii) Definition
> A nonentity is some thing that is not an entity?
>
> my comment: Note that ?entity? and ?thing? are synonyms.

Selective quoting is never a good way to try to make a point. The sentence before says "An entity is some thing in the modelled universe", i.e. a definition if "entity" in the current context. A thing that is not in the modelled universe is not an entity so the two words are not synonyms. Simple.

>
> (i) Definition
> Surrogates. A surrogate is a unique value assigned to each entity.
>
> my comment: The entity is the real world object and it is not possible
> to assign value to the real world object.

I can assign value to anything I choose. I can make my system assign *a* value to its representation of an entity. There are two distinct meanings of "value" there. Either way your comment is just wrong.

> (iii) Definition
> The RM/T addresses atomic semantics by?
>
> my Comment: With the most carefully observing the RM / T, one could not
> find a single atom of the semantics, because in the RM/T, section 4,
> E. Codd wrote: "Database users may cause the system to generate or delete
> a surrogate, but they have no control over its value, nor is its value
> ever displayed to them.?

There are various things one could say about Codd's statement you have quoted, but what the blazes has it got to do with atomic semantics? I suspect that you have totally misunderstood the meaning of "atomic semantics" in the context of that web page.

Or, to put it another way, nothing you are saying makes any sense at all.

Eric

-- 
ms fnd in a lbry
Received on Mon Nov 05 2012 - 22:44:14 CET

Original text of this message