Morpheme structure rules capture the intimate connection between the phonological redundancy of a language and the constraints it exhibits on phoneme sequences in its morphemes. Infact, a morpheme structure rule can be interpreted both as a statement of a constraint on phoneme sequences and as an algorithm for predicting redundant feature values in phoneme sequences [...]. Thus, a full set of phoneme structure rules for a language will do two things: it will state, in term of features, all constraints on what sequences of phoneme are possible in morphemes, and it will allow each morpheme to have a representation in which redundant feature values are omitted.
- Stanley (2004), Pag. 43-44

The morpheme structure (MS) rules [...] do not map one level of representation onto another, but rather state the redundancies that exist at a single level, the systematic phonemic level.
- Stanley (2004), Pag. 45