# File lib/ruote/dboard/process_status.rb, line 101
    def root_expressions

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

      roots = roots.each_with_object({}) { |e, h|
        h["#{e.h.fei['expid']}__#{e.h.fei['subid']}"] = e
      }

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