For example, RTS tagset uses one tag (RP) to cover a range of particles which are subdivided to nine subclasses by MADA (part det, part focus, part fut, part interrog, part neg, part restrict, part verb, part voc ,part); and it uses several tags to distinguish between verbs tenses (VBD, VBG, VBN, VBP) where MADA just uses one tag (verb).
mapping between these tagsets is a prerequisite for using agreement-based method on the taggers' outputs.