tailieunhanh - Báo cáo khoa học: "Abstract Finite-State Morphology"

Aspects of abstract finite-state morphology are introduced and demonstrated. The use of two-way finite automata for Arabic noun stem and verb root inflection leads to abstractions based on finite-state transition network topology as well as the form and content of network arcs. Nonconcatenative morphology is distinguished from concatenative morphology by its use of movement on the output tape rather than the input tape. The idea of specific automata for classes of inflection inheriting some or all of the nodes, arc form and arc content of the abstract automaton is also introduced. . | On Abstract Finite-State Morphology Ajit Narayanan Lama Hashem Department of Computer Science University of Exeter Exeter EX4 4PT UK Abstract Aspects of abstract finite-state morphology are introduced and demonstrated. The use of two-way finite automata for Arabic noun stem and verb root inflection leads to abstractions based on finite-state transition network topology as well as the form and content of network arcs. Nonconcatenative morphology is distinguished from concate-native morphology by its use of movement on the output tape rather than the input tape. The idea of specific automata for classes of inflection inheriting some or all of the nodes arc form and arc content of the abstract automaton is also introduced. This can lead to novel linguistic generalities and applications as well as advantages in terms of procedural efficiency and representation. 1 Introduction Finite-state approaches to morphology provide ways of analyzing surface forms by appealing to the notion of a finite-state transducer which in turn mimics an ordered set of rewrite rules. Instead of intermediate forms being introduced as would happen if rewrite rules are used . Narayanan and Mehdi 1991 for Arabic morphology the finite-state transducer works on two tapes one representing lexical structure the other the surface structure and switches states if the symbols currently being scanned on the two tapes match the conditions of the state transition. Following the distinction expressed by Kay 1987 two-level morphology is a specialization of finite-state morphology in that intermediate forms are not required even in the grammatical formalism . Koskenniemi 1983 Koskenniemi 1984 . The only representations required are those for the lexical and surface forms together with ways of mapping between the one and the other directly. Surface forms express the result of any spelling-change interactions between dictio-nary lexicon primitives. A typical architecture of a two-level morphological .