Abstract: Parallel programming is difficult. The need for correct and efficient parallel programs is important and one way to meet this requirement is to work on the refinement chain. Beginning with a specification written in TLA/sup +/ (for instance), we can transform it-or refine it-into finer grained specifications. At some step, enough structure will have appeared so that we can bridge a gap to fill this structure. We introduce a more concrete version of TLA/sup +/, CTLA, where structuring concerns are to be expressed, but where distributing, mapping or implementation problems are avoided. Indeed, we firmly believe that it is a mistake to go immediately from TLA/sup +/ to a real language like CC++, since the ditch is still too wide. A numerical example supports our claim.