      \fitem{is_exec}(\vValue): the predicate returns true if the
      argument represents an \emph{exec}, that is, the instance of a
      compound action (especially the result of a process call). The
      predicate returns true even if the compound action has finished
      its computation. However, the \emph{exec} itself used in a boolean
      condition evaluates to true if the compound action is still
      running and false elsewhere.



      %%% -------------------------------------------------------

