pool::FileDescriptor Node1 pool::FileDescriptor + FileDescriptor() + FileDescriptor() + PFN() + setPFN() + FID() + setFID() + dbc() + dbc() + setDbc() Node2 std::string Node2->Node1 -m_FID -m_PFN Node3 std::basic_string< char > Node3->Node2 Node4 pool::DatabaseConnection + name() + type() + handle() + handle() # ~DatabaseConnection() Node4->Node1 -m_DBC