A taxonomy is a classifying device. There are essentially two types of taxonomies. The first is the non-hierarchial one, which is used to keep similar things together. The classification of English textbooks by subject, e.g., literature, spelling, and grammar would be non-hierarchial. The second is the hierarchial one, which is used to classify elements along some continuum. The classification of English literature books according to the relative difficulty of vocabulary would be hierarchial. The latter type can be most useful for viewing the organization of a system of things or activities and is used toward those ends in this study, although in this chapter examples of both types are given.
George Hirshfield (Mon,) studied this question.