Re: What is that "more" that makes E-R model truly independent ?
From: Jon Heggland <jon.heggland_at_idi.ntnu.no>
Date: Tue, 24 Jul 2007 14:54:49 +0200
Message-ID: <f84sqj$lse$1_at_orkan.itea.ntnu.no>
Date: Tue, 24 Jul 2007 14:54:49 +0200
Message-ID: <f84sqj$lse$1_at_orkan.itea.ntnu.no>
David Cressey wrote:
> An E-R model does not have foreign keys installed. Relationships are
> diagrammed by lines between boxes, but they are not implemented via foreign
> keys. This help keep the diagram unbiased, because there are other ways,
> besides foreign keys of implementing relationships. In a relational model,
> foreign keys are used to implement relationships. (some modellers deviate
> from what I'm saying here, but this is the formal description)
This is formal? What is the formal definition of a relationship?
-- JonReceived on Tue Jul 24 2007 - 14:54:49 CEST