This paper discusses the problem of drawing a boundary between morpholexical and morphophonemic phenomena within a generative model of phonology. Criteria for classifying alternations are set down and rules are examined in light of these criteria. (CHK)

The autosegmental rule of vowel harmony (VH) in Palestinian Arabic is shown to be constrained simultaneously by metrical and segmental boundaries. The indicative prefix bi- is no longer an exception to VH if a structure is assumed that disallows the prefix from sharing a foot with the stem, consequently blocking VH. (Author/LMO)