The selected POS pairs were transformed into compound tags.
we generated three sets of POS units by this process: the original POS set without the compound unit (Base), the original set and an additional 50 compound units (Base+mi50), and the original set and an additional 110 units (Base+mi110   For each ngram, three sets of VSMs were built using three sets of tags as terms, yielding a total of nine VSMs.