OK, but for me is desiderable to suspend execution of the SUB-PROCESS: what I need is to transition the root-process to a "SUSPEND" state (please, see the image at the begin of the original post).
Perhaps If execution suspension is not the solution this is not a big problem for me (this reasoning was born because the pvm forbid me to signal the main process that contains the wait state, so i was trying to suspend the sub-process and see what would happen! :) ).
Your idea is somewhat vague for me, maybe I don't understand the concept of wait state as you intend it, but: if every signal in the main-process execution, outside the sub-process nodes will cause an exception (until the sub-process instance is ended, of course , how we can "move to a wait state"? you intend a fork before entering any sub-process node?