Comparing Lexicalized Treebank Grammars Extracted From Chinese, Korean, And English Corpora

In this paper, we present a method for comparing Lexicalized Tree Adjoining Grammars extracted from annotated corpora for three languages: English, Chinese and Korean. This method makes it possible to do a quantitative comparison between the syntactic structures of each language, thereby providing a way of testing the Universal Grammar Hypothesis, the foundation of modern linguistic theories. 1 I n t r o d u c t i o n The comparison of the grammars extracted from annotated corpora (i.e., Treebanks) is important on both theoretical and engineering grounds. Theoretically, it allows us to do a quantitative testing of the Universal Grammar Hypothesis. One of the major concerns in modern linguistics is to establish an explanatory basis for the similarities and variations among languages. The working assumption is tha t languages of the world share a set of universal linguistic principles and the apparent structural differences attested among languages can be explained as variation in the way the universal principles are instantiated. Comparison of the extracted syntactic trees allows us to quantitatively evaluate how similar the syntactic structures of different languages are. From an engineering perspective the extracted grammars and the links between the syntactic structures in the grammars are valuable resources for NLP applications, such as parsing, computational lexicon development, and machine translation (MT), to name a few. In this paper we first briefly discuss some linguistic characteristics of English, Chinese, and Korean, and introduce the Treebanks for the three languages. We then describe a tool that extracts Lexicalized Tree Adjoining Grammars (LTAGs) from Treebanks and the results of its application to these three Treebanks. Next, we describe our methodology for automatic comparison of the extracted Treebank grammars, This consists primarily of matching syntactic structures (namely, templates and sub-templates) in each pair of Treebank grammars. The ability to perform this type of comparison for different languages has a definite positive impact on the possibility of sorting out the universal versus language-dependent features of languages. Therefore, our grammar extraction tool is not only an engineering tool of great value in improving the efficiency and accuracy of grammar development, but it is also very useful for investigating theoretical linguistics. 2 T h r e e L a n g u a g e s a n d T h r e e ' r r e e b a n k s In this section, we briefly discuss some linguistic characteristics of English, Chinese, and Korean, and introduce the Treebanks for these languages. 2.1 T h r e e Languages These three languages belong to different language families: English is Germanic, Chinese is Sino-Tibetan, and Korean is Altaic (Comrie, 1987). There are several major differences between these languages. First, both English