Currently, there is no specific plan to provide a collective interface in the ADI, other than what is present in the function interface in the MPICH implementation (see src/coll/intra_fns.c. However, there will be some additional routines for communicator/context id management (as part of a separate effort to reduce the cost of handling MPI_COMM_WORLD and its duplicates). In fact, the interfaces provided by the first generation ADI (e.g., MPID_Barrier) are removed in favor of the MPIR_COLLOPS structure (which is in the MPICH implementation, not the ADI).
This is not meant to preclude the development of extensions to the ADI to support collective operations. In fact, such support is essential. However, the exact nature of this support requires additional research. One possibility is to provide support for simple barrier, broadcast, and gather operations. Other approaches might provide ways to optimize the point-to-point implementations. The interaction of the collective information with the topology of the physical ( not logical) interconnect (and hence ADI support for MPI's topology routines) must also be taken into account. Because of the number of issues involved, ADI support for collective operations is left to a later note.