[boost] [tree] associative containers

I've been studying the tree proposal to see how I could write adaptors in my tree_node library (now at version 0.2 in the sandbox) that conform to the current concepts. Is there anything in the proposal that is analogous to a PairAssociativeContainer?  My tree_node library defines an AssociativeTreeNode concept and a couple of models that I've found to be useful, e.g. for implementing decision tree learning algorithms. Cromwell D. Enage