Re: Question about modeling

"mathmoi" <mathieu.page_at_gmail.com> wrote in message news:1107461386.603251.160360_at_c13g2000cwb.googlegroups.com...

> First, i'd like to thank you for your help. It is _really_ appreciated.

Thank you for your kind words. I haven't contributed anything to the solution yet.
All I'm doing at this stage is clarifying the requirements.

> I read your post... twice and it seem to me that you got it right. You
> defined the problem well.

Thanks again. But I'm not satsified yey that I've defined the problem well. The fact that I suggested 8 tables
(4 for entities and 4 for relationships) while your solution has only 4 tables suggests to me that I still need to clarify the requirements some more.

In particular, my last suggestion was probably too flexible.

> I have implemented a solution (That, I must admit, do not look nice to
> me). Here is what I actualy have:

> CLIENTS (CLIENTS_ID*, ...)
> DEPARTMENTS (DEPARTMENTS_ID, CLIENT_ID (FK), ...)
> CONTRACTS (CONTRACTS_ID, CLIENT_ID (FK), ...)

> Then I have this table doing a link between DEPARTEMENTS AND CONTRACT

> CONTRACTS_DEPARTEMENTS(CONTRACTS_ID*, DEPARTEMENTS_ID*, CLIENT_ID (FK
> of both DEPARTMENTS and CONTRACTS))

> So ! Now I have the contracts attached to the client and I also use
> this FK in the relation with the DEPARTEMENTS table. So I can not have
> a contract shared among departments of different clients. What I do not
> like in this solution is that I duplicated the fact that a contract
> belong to wich client. There is now two way to look it out : 1) Look at
> the CLIENT_ID attribute of CONTRACTS, 2) Follow a link from a contact,
> to a departments, to a client. But, maybe it is the thing to do and I
> should not worry at all.

> In any case, I would like to know what is your solution.

I believe, although I'm not sure, that your solution is as good as the one I will come up with when I finish clarifying the requirements.

> Again, thanks for your help and I hope I am clear, english is not my
> primary language and I fear I'm a better english reader than writer.

No problem at all! If your primary language is French, then according to my mother, your primary language is quite a bit more precise than mine is. In particular, I think the French word "Informatique" conveys a much more precise concept than the English phrase "Information Technology". But we'll do the best we can with English.

If you would like to pursue this further, my next step was going to be to model the department as a sub-entity of the client. The main effect of this would be to reduce the number of tables from 8 to 7, and to enforce the rule that

"A client may have several departments, but a department can belong to exactly one client."

Your solution permits, if I have read it correctly, that a department could exist without any client. Of course, such a department could never participate in any contracts, but maybe it's good to forbid such a department to begin with.

Is this worth pursuing? Received on Fri Feb 04 2005 - 15:29:25 CET