Re: What is a Relationship !?

Tom Hester wrote:

>"Lauri Pietarinen" <lauri.pietarinen_at_atbusiness.com> wrote in message
>news:bpjfpo$vre$1_at_nyytiset.pp.htv.fi...
>
>
>>Tom Hester wrote:
>>
>>
>>
>>OK, but perhaps the database was for a labour pension company, whose
>>main function is to track
>>peoples employment history over the years and the concept of an
>>employment is essential. Is it a relationship then?
>>
>>
>You seem to think that relationships are somehow less valued--or less
>essential--than entities? That is certainly not the case.
>
No I don't. I just think there is no reason to make a distinction between them.

>>If we can get along with one concept (entity) instead of two (entity,
>>relationship), why should we introduce this extra concept??
>>
>>
>The difference between entities and relationships is often important in
>object modeling. If all you are doing is a relational model in isolation of
>any process model, you're right it probably doesn't make any difference; but
>I can't imagine why you would do that!
>
OK. If identiffying relaitonships is important for object modeling, then it's fine for me. I just have managed to get by without E/R (and used only "E"-modelling) for over 10 years, but maybe I am doing something wrong...

>>The danger I see in E/R modelling is that N:M relationships are "left
>>alone" for too long in the process
>>resulting in nasty surprices down the road.
>>
>>
>I'm not pushing ER as opposed to relational modeling. I merely attempted to
>answer a question that seemed to have been asked in good faith. If your
>claim is that ER modeling does not capture sufficient data semantics, then I
>absolutely agree. However, I think that relational modeling is only
>marginally better...
>
OK.

Lauri Pietarinen Received on Fri Nov 21 2003 - 14:53:56 CET