Re: One-To-One Relationships

On 2 dec, 16:10, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
> 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?

Since the objects and the fact-types in ORM are basically the same thing as entities and relationships in ER.

• Jan Hidders