[Boost-users] bimap: one to many

Hello I want a collection to store a relationship N to M like so: Item of type A Item of type B A1 B1,B2,B3 A2 B4 A3 B1 and I would like a convenient way to get from a A instance to the list of B instances, and vice versa, from a given B instance to the list of A instances. At runtime, the A objects are created first, then a list of B objects is created. Later, B objects get modified asynchronously and that modification need to update the relevant A instances what container to use? boost::bimap< unordered_set , unordered_set > ?