[Part IV. Tools and methodology, UNIDIA]
UNIDIA is a database on sound change designed to compile the sound change hypotheses formulated to account for the phonological evolution of the languages of the world. It aims at deriving a data-based typology of sound change, universals, tendencies and sound change distributions. It now contains about 3750 sound changes for some 190 languages, essentially sampled from the Bantu, Sinitic and Daic language groups. This data can be explored based on various phonetic criteria, and sound change distributions can be represented on a geographical map or on a language family tree. At completion, UNIDIA should be representative of how phonological evolution is construed by the community of historical linguists and could become a useful tool for testing competing models of language evolution.