When discussing MPI procedures the following semantic terms are used. The term message data buffer refers to the send/receive buffer used in a communication procedure. The term file data buffer refers to the data buffers used by MPI I/O procedures. In this section we use the term data buffer and depending on the MPI procedure it will refer to message data buffer or file data buffer. sec:lang:semantics:summary shows how the terms defined in this section apply to all operation-related MPI procedures.