A Quasi-Dependency Model for the Structural Analysis of Chinese BaseNPs

A Quasi-Dependency Model for Structural Analysis of Chinese BaseNPs* Zhao Jun Huang Changning Department of Computer Science & Technology, The State Key Lab of Intelligent Technology & Systems, Tsinghua University, Beijing, China, 100084 Email: zj@sl000e.cs.tsinghua.edu.cn, Hcn@tsinghua.edu.cn Abstract: The paper puts forward a quasi- dependency model for structural analysis of Chinese baseNPs and a MDL-based algorithm for quasi- dependency-strength acquisition. The experiments show that the proposed model is more suitable for Chinese baseNP analysis and the proposed MDL- based algorithm is superior to the traditional ML- based algorithm. The paper also discusses the problem of incorporating the linguistic knowledge into the above statistical model. 1. Introduction The concept of baseNP is initially put forward by Church. In English, baseNP is defined as 'simple non-recursive noun phrases', which means that there is no sub-noun-phrases contained in a baseNP[1]. B~t the definition can not meet the needs in Chinese information retrieval. The noun phrases such as "1~ ~(natural) ~-~(language) ~(process)", "~-IF~b~l(Asian) ~;-'~!]~(finance) ~f~ ~(crisis)" and "i~(political) /¢~k$1J(system) ~(reformation) ~.~(process)" are critical for information retrieval, but they are not non- recursive noun phrases. Type In Chinese, the attribute of noun phrases can be classified into three types, that is restrictive attributes, distinctive attributes and descriptive attributes, among which the restrictive attributes have agglutinative relation with the heads. The paper defines the Chinese baseNP using the restrictive attributes. [ Definition 1 ] Chinese baseNP (hereafter abbreviated as baseNP)- baseNP -- baseNP + baseNP baseNP --- baseNP + N I VN baseNP -- restrictive-attribute + baseNP baseNP --- restrictive-attribute + N I VN restrictive-attribute --- A I B I V IN ] S I X I (M+Q) Where, the terminal symbols A, B, V, N, VN, S, X, M, Q stand for respectively adjective, distinctives, verbs, nouns, norminalized verbs, locatives, non- Chinese string, numerals and quantifiers. According to the definition, noun phrases falls into baseNPs and non-baseNPs (abbreviated as ~baseNP). Table-1 gives some examples. Table- 1 : Examples of baseNP and -baseNP Examples BaseNP ~ q~/air z-I~/eorridor BaseNP i~'~/politics/t~k$1J/system ~/reform BaseNP ,W, D/export ~ h/commodity ffl'~/price ~/index baseNP ~,/complicated I~/de ~fi~q-'/feature - baseNP ~i)~/research -~/and ~J~/development -baseNP ~i~l~/teacher q/write t~/de i,~/eomment Both baseNP recognition and baseNP structural analysis are basic tasks in Chinese information retrieval. The paper mainly discusses the problems in structural analysis of baseNPs, which is essential for generating the compositional indexing units from a baseNP. The task of baseNP • The research is supported by the key project of the National Natural Science Foundation 1 structural analysis is to determine the syntactic structure of a baseNP. In this paper, we use dichotomy for baseNP analysis. For example, the structure of "I~1 ~/natural ~/ianguage ~J~ /process" is "( ~ ~/natural i,~'/language) ~ /process". Obviously, a baseNP composed of three or more than three words has syntactic ambiguities. For example, baseNP "x y z" has two possible structures, that is "(x y) z" and "x (y z)". The task of baseNP structural analysis is to select the correct structure from the possible structures. The paper …

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