Two-Level Morphology: A General Computational Model for Word-Form Recognition and Production

This dissertation presents a new computationally implemented linguistic model for morphological analysis and synthesis. The model incorporates a general formalism for making morphological descriptions of particular languages, and a language-independent program implementing the model. The two-level formalism and the structure of the program are formally defined. The program can utilize descriptions of various languages, including highly inflected ones such as Finnish, Russian, or Sanskrit. The new model is unrestricted in scope and it is capable of handling the entire language system as well as ordinary running text. A full description of Finnish inflectional morphology is presented in order to validate the model.
The two-level model is based on a lexicon system and a set of two-level rules. It differs from generative phonology in the following respects. The rules are parallel, as opposed to being sequentially ordered, as is the case with the rewriting rules of generative phonology. The two-level model is fully bidirectional both conceptually and processually. It can also be interpreted as a morphological model of the performance processes of word-form recognition and production. The model and the descriptions are based on computationally simple machinery, mostly on small finite state automata. The computational complexity of the model is discussed, and the description of Finnish is evaluated with respect to external evidence from child language acquisition.