Are circular relationships a bad thing in ER-modeling?

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)

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

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.

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?

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?

Thanks for any input on this!!

Tor Arne Received on Mon May 03 2004 - 15:23:09 CEST