The notation is standard in the literature AFAIK: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.24.3698&rep=rep1&type=pdf http://citeseerx.ist.psu.ed

The notation is standard in the literature AFAIK: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.24.3698&rep=rep1&type=pdf http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.24.... FSTs are commonly used for morphological analysis, and AFAIK, there isn't much cross pollination between those folks and folks that use FSTs more as data structures of large sets or maps. So there's probably a bit of a communicative mismatch.