Some of their models are also Tverskyan ratio models.
to see this, we divide (9) everywhere by σ(w 1 , w 2 ): If the SI is MIN, then the two terms in the denominator are the inverses of what W&W call difference-weighted precision and recall: REC(w 1 , w 2 ) = σMIN (w 1 ,w 2 ) σMIN (w 2 ,w 2 ) , So for t MIN , (9) can be rewritten: t MIN is a weighted harmonic mean of precision and recall, the so-called weighted Fmeasure (Manning and Schütze, 1999).