[Boost-users] boost.graph external properties question.

HI, I'm starting a project that uses boost.graph and I'm trying to decide if I should use internal or external properties. My code that implements external properties is like, for example: typedef boost::graph_traits <GraphT>::vertex_descriptor Vertex; typedef std::map<Vertex,Vertex_Datum,ltDescriptor<Vertex> > VertexData; My question is: Given my use of Vertex as a key of a std::map, it needs to be unique. Is this uniqueness quality maintained across different graphs? That is, can I instanciate 2 GraphT objects and populate both, but maintain only one VertexData container? Assume that I am not defining any internal properties in GraphT.