[Boost-users] How to represent bipartite graphs ?

Hello together, in my software I have to represent bipartite graphs, in my case petri nets (two disjoint sets - the places and the transitions - and only links between elements of the disjoint sets). I would like to use BGL for this purpose, but I did not find a "nice" solution for this problem. I am quit new to BGL and the only way I see is representing the two types of vertices inside a vertex-property. A better way would be to have two types of vertex properties, but I think this is not possible. Is there anyone who has a solution or an idea for this kind of problem? Thanks and best regards Markus