['he', 'keep', 'half', 'EmptyParameter', 'EmptyParameter']
['<PRP>', 'keep-15.2', "Synset('fraction.n.03')", 'EmptyParameter', 'EmptyParameter']
There must be a vault on-board, offering to show them where to find it if he can keep half of the gold therein.
there must be a Synset('propulsion.n.02') on-board, offering to show <PRP> where to find <PRP> if <PRP> can keep Synset('fraction.n.03') of the Synset('value.n.02') therein.