The MPI collective and topology routines can benefit from information  about the topology of the underlying interconnect.  Unfortunately, there is no best form for the representation (the MPI-1 Forum tried to define such a representation, but was unable to).  One useful decomposition that has been used in cluster enviroments is a hierarchical decomposition. The other obviously useful topology information would match the needs of  \texttt{MPI_Cart_create}.  However, it may be simpler to for the device to  implement this routine directly. Other useful information could be the topology information that matches the needs of the collective operation, such as spanning trees and rings. These may be added to ADI3 later. Question: Should we define a cart create function?  Dims create?\subsection{Usage} This routine has nothing to do with the choice of communication method that a implementation of the ADI may make.  It is intended only to communicate information on the heirarchy of processes, if any, to  the implementation of the collective communication routines.  This routine may also be useful for the MPI Graph topology functions.