With these notations, RD(q, s) is true if and only if is true for some w h , w d |q , for some u h , u d |s and for some i and j. EQ(w h , u h )∧EQ(w d , u d ) requires that the question dependency w h , w d |q and the snippet dependency u h , u d |s match; w h ∈ m (i) ∧ w d ∈ m (j) requires that the head word and dependent word are in the i th -rank and j th rank MMP, respectively.
rD(q, s) is a dependency feature enhanced with MMPs.