weak entity
From: Ashutosh Galande <galande_at_uiuc.edu>
Date: Tue, 8 Oct 2002 02:19:07 -0700
Message-ID: <Gnxo9.34396$m7.318065_at_vixen.cso.uiuc.edu>
Hi,
Date: Tue, 8 Oct 2002 02:19:07 -0700
Message-ID: <Gnxo9.34396$m7.318065_at_vixen.cso.uiuc.edu>
Hi,
While modeling a real life system it seems that its almost always possible to convert a weak entity into a strong entity by adding an "ID" attribute to it. (where ID is an external unique number which might not be a natural descriptor/attribute of the entity but still can be used to identify each entity instance uniquely eg: flight ID, item ID, book No, etc) So is there any golden rule or guideline which states when an entity should be kept weak and when an external attribute should be/can be added to it?
TIA
Ashutosh.
Received on Tue Oct 08 2002 - 11:19:07 CEST