# File lib/ruote/exp/flow_expression.rb, line 980
    def pre_apply_child(child_index, workitem, forget)

      child_fei = h.fei.merge(
        'expid' => "#{h.fei['expid']}_#{child_index}",
        'subid' => Ruote.generate_subid(h.fei.inspect))

      h.children << child_fei unless forget

      msg = {
        'fei' => child_fei,
        'tree' => tree.last[child_index],
        'parent_id' => forget ? nil : h.fei,
        'variables' => forget ? compile_variables : nil,
        'workitem' => workitem
      }
      msg['forgotten'] = true if forget

      msg
    end