A person wearing khaki pants climbing up the side of a rocky cliff.
A person is climbing up a cliff.
A person is climbing up a cliff is a rephrasing of a person wearing khaki pants climbing up the side of a rocky cliff.  It's also actually a sentence, whereas a person wearing khaki pants climbing up the side of a rocky cliff is not a sentence (it contains no verb).
exists e1 e2 s1 s2 s3 x1 x2 x3 x4 x5 x6.(n_side(x5) & a_topic(x1) & Theme(e2,x3) & Actor(e2,x2) & v_wear(e2) & a_up(s3) & Manner(e1,s3) & Theme(e1,x5) & Actor(e1,x4) & v_climb(e1) & of(x5,x6) & n_cliff(x6) & a_rocky(s2) & Theme(s2,x6) & (x3 = x4) & n_pants(x3) & a_khaki(s1) & Theme(s1,x3) & (x1 = x2) & n_person(x1))
exists e1 s1 x1 x2.(a_up(s1) & Manner(e1,s1) & Theme(e1,x2) & Actor(e1,x1) & v_climb(e1) & n_cliff(x2) & n_person(x1))