If one annotation (say α s ) is more learnable than the other (with respect to p, l) in a relative portion r of these pairs, we say that p is r-biased towards α s with respect to l. If for some s ∈ S, it holds that for every p ∈ P, l ∈ L, p is r-biased (r ≫ 0.5) with respect to l towards the same annotation (say, α s ), we say there is a unanimous r-bias towards α s .
α s is the empirically preferred annotation of s. Varying syntactic structures are prevalent in many syntactic formalisms (see Section 7).