This model has been popular for language modelling and bilingual word alignment, and an implementation with improved inference called mkcls (Och, 1999) 1 has become a standard part of statistical machine translation systems.
each table at one level is equivalent to a customer at the next deeper level, creating the invariants: where u = t l−1 indicates the unigram backoff context of h. The recursion terminates at the lowest level where the base distribution is static.