The category "<user_dialog_command-command>" can be expressed as follows:
<assertion-command-existence_claim>
<existence_claim-inv-gapsout_null-gapsin_null>
<np-gapsout_null-gapsin_null-wh> <aux-can> <basic_nl_command-command-gapsout_null-gapsin_np_gap>
<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>