Hi Jean-Marc,
thanks for your feedback! I would very much like to use some RPC mechanism to communicate between PI and some external program. There would be many mechanisms for doing so, such as JSON or XML-RPC. But given the huge API that PI has, this might be an equally huge task. Being able to use PI from "outside" would also be great (making all the power of PI available to Python, R, C#, Java,...), but that also requires to RPC a significant part of PI's API.
Currently I am looking into a module that simply communicates via command line options and shared FITS files with PI always being the master, basically doing in PCL what you suggested for PJSR. Not the most elegant/performant/versatile method, but sufficient in many cases, and it would give us undo, scriptability, process containers, image containers, previews, ... - a lot of which are not fully supported in PJSR.
Georg
