Dependency Parsing of Japanese Spoken Monologue Based on Clause Boundaries

Proceedings of the 21st International Conference on Computational Linguistics and 44th Annual Meeting of the ACL, pages 169–176, Sydney, July 2006. c⃝2006 Association for Computational Linguistics Dependency Parsing of Japanese Spoken Monologue Based on Clause Boundaries Tomohiro Ohno†a) Shigeki Matsubara‡ Hideki Kashioka§ Takehiko Maruyama♯ and Yasuyoshi Inagaki♮ †Graduate School of Information Science, Nagoya University, Japan ‡Information Technology Center, Nagoya University, Japan §ATR Spoken Language Communication Research Laboratories, Japan ♯The National Institute for Japanese Language, Japan ♮Faculty of Information Science and Technology, Aichi Prefectural University, Japan a)ohno@el.itc.nagoya-u.ac.jp Abstract Spoken monologues feature greater sen- tence length and structural complexity than do spoken dialogues. To achieve high parsing performance for spoken mono- logues, it could prove effective to sim- plify the structure by dividing a sentence into suitable language units. This paper proposes a method for dependency pars- ing of Japanese monologues based on sen- tence segmentation. In this method, the dependency parsing is executed in two stages: at the clause level and the sen- tence level. First, the dependencies within a clause are identified by dividing a sen- tence into clauses and executing stochastic dependency parsing for each clause. Next, the dependencies over clause boundaries are identified stochastically, and the de- pendency structure of the entire sentence is thus completed. An experiment using a spoken monologue corpus shows this method to be effective for efficient depen- dency parsing of Japanese monologue sen- tences. 1 Introduction Recently, monologue data such as a lecture and commentary by a professional have been consid- ered as human valuable intellectual property and have gathered attention. In applications, such as automatic summarization, machine translation and so on, for using these monologue data as intel- lectual property effectively and efficiently, it is necessary not only just to accumulate but also to structure the monologue data. However, few at- tempts have been made to parse spoken mono- logues. Spontaneously spoken monologues in- clude a lot of grammatically ill-formed linguistic phenomena such as fillers, hesitations and self- repairs. In order to robustly deal with their extra- grammaticality, some techniques for parsing of di- alogue sentences have been proposed (Core and Schubert, 1999; Delmonte, 2003; Ohno et al., 2005b). On the other hand, monologues also have the characteristic feature that a sentence is gen- erally longer and structurally more complicated than a sentence in dialogues which have been dealt with by the previous researches. Therefore, for a monologue sentence the parsing time would in- crease and the parsing accuracy would decrease. It is thought that more effective, high-performance spoken monologue parsing could be achieved by dividing a sentence into suitable language units for simplicity. This paper proposes a method for dependency parsing of monologue sentences based on sen- tence segmentation. The method executes depen- dency parsing in two stages: at the clause level and at the sentence level. First, a dependency rela- tion from one bunsetsu1 to another within a clause is identified by dividing a sentence into clauses based on clause boundary detection and then ex- ecuting stochastic dependency parsing for …

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