We define the syntactic score for all sentences in s as: where Dep(s) are the dependency parse trees for all sentences in s; L Dep is a 3-gram language model over dependency triples which gives the likelihood of an arc label l being used between a pair of words (w i , w j ).
for example in figure 2, the syntactic compatibility score includes dependency likelihoods of the Syn function prefers stories s that (a) have similar dependency structure to the original story s and (b) make use of a common syntactic configuration.