Re: Are circular relationships a bad thing in ER-modeling?

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"xlazyx" <nope_at_nope.com> wrote in message news:c75h6n$otf$3_at_orkan.itea.ntnu.no...
> Hey!
>
> If I have the following theatre system:
>
> A theater sets up _shows_, which is based on a _manuscipt/play_ written by
a
> _person_ A show also has _persons_in differnent _roles_, based on the
> _manuscript_.
>
> And have the following entities:
>
> Theater(TheaterID, Name)
> Manuscript(ManuscriptID, Name, Year)
> Person(PersonID, Name)
> Show(ShowID, ManuscriptID, TheaterID, Date, Time)
> Role(RoleID, ManuscriptID, Name)

Show is an ENTITY or a RELATIONSHIP ? :-)

> How do I relate a Person to a show, so that a person can be an actor in a
> show, in multiple roles?

A Role in a Show can be played by multiple Persons ? How do you relate a Role to a Show ?

> And how do I relate a Person to a Manuscript, so that many people can
write
> the same manuscript, and one person can write serveral manuscripts.

What you usually use to relate two entities in ER-modeling ?

> As I see it I would end up with something like:
>
> Person->Show->Manuscript->Person, which is a circle relationship. Isn't
this
> bad? Or is it ok?

Bad for what purpose ?
Ok to whom ?
Circle? It looks like a triangle to me. :-)

> Of course, there has to be an entity between Person and Show because of
the
> N:N relationship, but that's not a problem right?

How do you relate a Person to a Role ?

> Thanks for any input on this!!
>
> Tor Arne

What deadline do you have ?

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