Dictionary expansion via phonological rules for a speech understanding system

This paper describes some modifications and extensions to the Bobrow-Fraser Phonological rule testing program (CACM 11, 1968, 766-772), which enable it to expand a dictionary of words read from a file and systematically try all possible combinations of optional rules, compute a running "probability" of a pronunciation as a function of probabilities of application and non-application of individual optional rules, associate arbitrary applicability tests with rules, and generate a summary table of which rules applied to each word and which words a given rule applied to. The system uses a notation similar to the classical Chomsky-Halle notation for phonological rules, and has been used to expand a 500-word dictionary for the BBN SPEECHLIS speech understanding system.