Finite-state Constraints

The two central problems in morphology are word formation and morphological alternations. The study of word formation is about the principles that govern the combinations of stems, affixes, and other types of morphemes. The problem of morphological alternations arises from the fact that a morpheme may have alternate realizations depending on its phonological environment and the composition of the word. Finite-state morphology is an attempt to account for these phenomena within the context of regular sets and regular relations. The claim that one of the problems can be solved in the finite-state state domain does not entail the same for the other, although the problems are certainly related. We concentrate here on morphological alternations, and put aside the question of word formation. We are primarily concerned with the type of rules used for describing morphological alternations and the principles of their application rather than the question of how morphemes should ideally be represented. The examples in this paper involve oldfashioned segmental representations but the main points apply equally well to feature-based and multi-tiered architectures.