The category "<user_dialog_command-user_response>" can be expressed as follows:
<assertion-user_response-existence_claim>
<existence_claim-inv-gapsout_null-gapsin_null>
<np-gapsout_null-gapsin_null-wh-pl> <existence_claim-pl-inv-gapsout_null-gapsin_np_gap>
<np-gapsout_null-gapsin_null-wh-sing> <existence_claim-sing-inv-gapsout_null-gapsin_np_gap>