The application of two-level morphology to non-concatenative German morphology

In this paper I describe a hybrid system for morphological analysis and synthesis. This system consists of two parts. The treatment of morphonology and non-concatenative morphology is based on the two-level approach proposed by Koskenniemi (1983). For the concatenative part of morphosyntax (i.e. affixation) a grammar based on feature-unification is made use of. Both parts rely on a morph lexicon. Combinations of two-level morphology with feature-based morphosyntactic grammars have already been proposed by several authors (c.f. Bear 1988a, Carson 1988, Görz & Paulus 1988, Schiller & Steffens 1989) to overcome the shortcomings of the continuation-classes originally proposed by Koskenniemi (1983) and Karttunen (1983) for the description of morphosyntax. But up to now no linguistically satisfying solution has been proposed for the treatment of non-concatenative morphology in such a framework. In this paper I describe an extension to the model which will allow for the description of such phenomena. Namely it is proposed to restrict the applicability of two-level rules by providing them with filters in the form of feature structures. It is demonstrated how a well-known problem of German morphology, so-called "Umlautung", can be described in this approach in a linguistically motivated and efficient way