lexical semantic variations (automobile sales, car sales), overlapping phrases (scheduling, real-time scheduling), or morphological variants like plurals (performance metric, performance metrics).
2 we propose a new approximate matching strategy Approx(k gold , k ext ) that accounts for morphological variants (Morph) and the two cases of overlapping phrases: either the extracted keyphrase includes the gold standard keyphrase (Includes) or the extracted keyphrase is a part of the gold standard keyphrase (PartOf).