Annotators were asked to perform phrase-tophrase alignments between abstracts and documents and to classify each alignment as either possible P or sure S, where P ⊆ S. In order to calculate scores for phrase alignments, we convert all phrase alignments to word alignments.
if we have an alignment between phrases A and B, then this induces word alignments between a and b for all words a ∈ A and b ∈ B.