Second, in the classical AP formula all relevant documents are considered relevant to the same extent.
we thus reformulate rel(f ) to give higher relevance to highly ranked features in |F V v |: where Incorporating these two modifications yields the APinc measure: Finally, we adopt the balancing approach in (Szpektor and Dagan, 2008), which, as explained in Section 2, penalizes similarity for infrequent words having fewer features (4 th property) (in our version, we truncated LIN similarity lists after top 1000 words).