The MPI-2 Standard, released in 1997, defined an interface for one-sided communication, also known as remote memory access (RMA). It was designed with the goal that it should permit efficient implementations on multiple platforms and networking technologies, and also in heterogeneous environments and non-cache-coherent systems. Nonetheless, even 12 years after its existence, the MPI-2 RMA interface remains scarcely used for a number of reasons. This paper discusses the limitations of the MPI-2 RMA specification, outlines the goals and requirements for a new RMA API that would better meet the needs of both users and implementers, and presents a strawman proposal for such an API. We also study the tradeoffs facing the design of this new API and discuss how it may be implemented efficiently on both cache-coherent and non-cache-coherent systems.