I've been googling for about two hours already but not successful yet so
I hope you guys can help me out.
I need some kind of n:m polymorphic relation like this:
building_types: living, shops
block_types: residential, commercial
activity_types: act1, act2
So now I need a connection table e.g. activity_scope so I can for
act1 only for living and residential and act2 for commercial and shops