"horses for courses"

[JonathanBlock]

Some subjects can only be taught by one specialist teacher.
Some subjects can be taught by several different teachers.

Some teachers can teach only one subject
Some teachers can teach multiple (but not all) subjects

Is there a way to create
a constraint/preference for teachers = subjects qualified to teach
and/or
a constraint/preference for subjects = teachers qualified to instruct?

[Liviu Lalescu]

Please follow this and subsequent answers on http://lalescu.ro/liviu/fet/forum/index.php?topic=1053

(duplicate initial post here).