The category "<embark_debark_command>" can be expressed as follows:

<embark_debark_command>

<intrans_embark_debark_verb-located> <location_mod>

<intrans_embark_debark_verb-not_located>

<trans_embark_debark_verb-located> <other_unit> <location_mod>

<trans_embark_debark_verb-not_located> <other_unit>