Re: A simple situation shows confusion about basic concepts

From: Ney André de Mello Zunino <zunino_at_undl.org.br>
Date: Tue, 26 Oct 2004 18:10:54 +0000
Message-ID: <2u7spkF26lnopU1_at_uni-berlin.de>


Laconic2 wrote:

>>KB
>>-------------------------
>>uc_id1        PK,FK
>>uc_id2        PK,FK
>>relationshipType
>>-------------------------

>
> I disagree. there could be more than one relationship type between the
> same two UC's.
>
> The PK is the whole relation, IMO.

Thank you for your replies, fellows. It seems I may have got you confused with the attribute 'relation_type' in the KB entity. That has nothing to do with relationships between tables in the database model. Its purpose is to specify the type of *conceptual* relationship the two UCs of a KB entry have, e.g. the concepts of "car" and "vehicle" have a "is a" relation_type. From his comment above, it seems Laconic2 understood it, while I am not so sure Kostas did. And yes, a pair of UCs may appear in more than one record in KB, as long as the relation type is different and that the first UC is not paired with itself.

Is there any other clarification I should add about the problem? My main goal is to understand the relationship (database level now) between those two entities. Which depends on which (if at all), whether it is a identifying or non-identifying or N:M relationship. In other words, I just want to make sure I get my design correct.

Thank you for your help,

-- 
Ney André de Mello Zunino
Received on Tue Oct 26 2004 - 20:10:54 CEST

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