Intersection Tables

Hi All

I’m relatively new to rails and ruby in general. I have a few questions
about conventions that should be used. I prefer to use postgresSQL as my
database backend and to follow standard conventions that I’ve been
taught and have used while designing several databases. Anyway, I was
reading this blog

I found it very helpful even though most of it was just review.

But I do have one question that I would like some other developers input
on. Is it a good idea to use concatenated primary keys for intersection
tables? Can anyone think of any circumstances underwhich an intersection
table would be referenced by another table?

I haven’t thought very hard on this yet, so I may be missing the
obvious. Any advice and/or opinions would be great.

Ciaou
Greg