La logique informatique
(selon les travaux de J.D WARNIER)
L.C.O The organization of companies
Data sets of a step :
Attention dear reader this is a true story !
If you look at the previous data model, it misses a relationship (maybe you've noticed it?) NO ? Then look at the operational model (corresponding) that we will be found in your computer system :
Here is the operational model of the database managed by your favorite DBMS !
In the operational database, you see the relationship Cdes d'expédition ---> Agencies, how does it happen? where is she from ?
This is a question i asked myself for 40 years !!! realize you !
40 Years of interrogation it's tiring .......
And then a day :
After having read and re-read the book L.C.O by J.D WARNIER, I came across this small definition by understanding the set of data relating to the shipping order, and I understood.
So let me explain :
?
In fact, when studying the set B of a logical database concerning a step, we do it in a totally disjoint way from the other stages of the system (I remind you that we bring back a complex problem to several simple problems).
The consequence is that a data set relating to a third party (in our example) may not to be concerned by the corresponding stream (s) of the step studied, and in this case at the time of studying the data sets relating to THIRD PARTIES, Exchanges and products of the step, this set has no reason to appear.
BUT, when studying the relations between sets, then we notice that there are relations that must be established on sets studied in other logical bases, and here, this is the case , remember the definition by understanding of our file "Every dispatch order concerns spare parts destined for an agency and only one", here is the relationship that was missing in our first schema, it did not leave from the hat ! (it's a french expression !)
And it is there that it is beautiful, remember the little sentence of which I spoke to you earlier:
The properties (or characteristics) stated in the definition in comprehension of a set are in fact only the statement of the relations existing between the studied set and the other sets defined in the system.
So do not forget when studying the sets of a step and the relationship between them, to note (in a corner!) The out-of-step relationships studied, due to certain properties of a definition by understanding.
Before finishing the organization of the data sets of a step, I would like to show you another way of representing the set B of a logical basis.