Walter's Weird Night<br>Walter noticed something strange in the sky one night. He didn't believe in space aliens, but he was confused. He was sure he had seen a flying saucer in the night sky. Then he saw on the news that a weather balloon had crashed. Walter was relieved that aliens hadn't come visiting after all.
Walter did not see a flying saucer.
Walter was sure he had seen a flying saucer, but then discovered a weather balloon had crashed, so that is what he actually saw. The wording 'sure he had seen' confused the model.
( z1 see :polarity - :ARG0 ( z2 person :name ( z3 name :op "Walter" ) ) :ARG1 ( z4 spaceship :ARG0-of ( z5 fly ) ) )