Some formal properties of phonological redundancy rules

Redundancy in this theory means that the specification (either + or -) of certain features of a phoneme is predictable given the specifications of certain other features of the same phoneme and/or of neighbouring phonemes of a phoneme sequence. These restrictions on feature specifications are usually expressed by "redundancy rules". E.g. in English all nasal phonemes voiced which is expressed by a rule ~+nasal] --~ are ~voice~, to be read as "each phoneme which is specified ~nasaq must also be specified E+voice~ ". Among the redundancy rules usually two main types are distinguishech Those like the one just mentioned which express a restriction valid for each phoneme of a language, independent of possible neighbouring phonemes, will be called "phoneme-structure rules" (P-rules) in this paper. Besides them, there are rules expressing restrictions on the admissible phoneme sequences of the language, e.g. English no ~+consonanta~ segment can follow a in morpheme-initial nasal; they will be called (as usual) "morpheme-structure rules" (M-rules). In the paper of STANLEY ~2] the former are called segment structure rules and the latter sequence structure rules. The aim of the present paper is to investigate the properties of phonoiogical redundancy rules on a mathe-