Re: One-To-One Relationships
Date: Sun, 02 Dec 2007 11:10:07 -0400
Message-ID: <4752cad3$0$5277$9a566e8b_at_news.aliant.net>
Jan Hidders wrote:
> On 1 dec, 15:03, JOG <j..._at_cs.nott.ac.uk> wrote:
>
>>[...] let me give an example as to why I find
>>the breakdown into entities and relationships deleterious. Say I have
>>two entity types staff_members and subjects, and a relationship
>>teaches:
>>
>>staff_member -- teaches --> subject
>>
>>This is all good and fine until a requirement changes that we need to
>>record the day the lecture is given on.
>
> Yes. Relationships may become Entities, Roles may become
> Relationships, Attributes may becomes Relationships, etc. As David
> remarked, there are ER dialects like ORM that smoothen this a bit, but
> you can never make that really go away. These problems have
> counterparts in the RM where foreign keys may become tables by
> themselves, or tables are split because a one-to-one relationship has
> become a one-to-many one.
ORM = ER ?!? Since when? Received on Sun Dec 02 2007 - 16:10:07 CET