A SimDM/Protocol represents software code that can be used to run astrophysical simulations or to post-process simulation results. A SimDM/Protocol defines the method by which SimDM/Experiment-s can be performed, like a blue-print, or template.  The SimDM/Protocol concept is separated out from the execution of its code in SimDM/Experiment, which allows us to reuse it for all experiments using the same code.
The concept is a direct gemeralisation of the concept by the same name in Martin Fowler's book "Analysis Patterns: Reusable Object Models" (Addison-Wesley Professional, 1996).