The attached idl looks like a very good start. But
some things remain a bit unclear (at least to me):

what exactly is a path ? How much 'style' and
similar state is associated with it ? What
attributes belong to a path, what belong to 
the DK ?

I'm still not convinced Path has to be an
interface. It could well be a struct (yeah, it's
a bit ugly, but surely much more efficient).