A security guard on watch duty at the museum.
The person is alert.
Being on watch as a security doesn't mean he is alert.
exists x1 x2 x3 x4 x5.(n_museum(x5) & a_topic(x1) & on(x1,x3) & at(x3,x5) & n_duty(x3) & of(x3,x4) & n_watch(x4) & n_guard(x1) & of(x1,x2) & n_security(x2))
exists s1 x1.(n_person(x1) & Theme(s1,x1) & a_alert(s1))