# File lib/ruote/engine/process_status.rb, line 70
    def root_expressions

      roots = @expressions.select { |e| e.h.parent_id == nil }

      roots = roots.inject({}) { |h, e|
        h["#{e.h.fei['expid']}__#{e.h.fei['sub_wfid']}"] = e; h
      }

      roots.keys.sort.collect { |k| roots[k] }
    end