Annotating Discourse Connectives in the Chinese Treebank

Proceedings of the Workshop on Frontiers in Corpus Annotation II: Pie in the Sky, pages 84–91, Ann Arbor, June 2005. c⃝2005 Association for Computational Linguistics Annotating Discourse Connectives in the Chinese Treebank ∗ Nianwen Xue Department of Computer and Information Science University of Pennsylvania xueniwen@linc.cis.upenn.edu Abstract In this paper we examine the issues that arise from the annotation of the discourse connectives for the Chinese Discourse Treebank Project. This project is based on the same principles as the PDTB, a project that annotates the English discourse con- nectives in the Penn Treebank. The pa- per begins by outlining range of discourse connectives under consideration in this project and examines the distribution of the explicit discourse connectives. We then examine the types of syntactic units that can be arguments to the discourse connectives. We show that one of the most challenging issues in this type of dis- course annotation is determining the tex- tual spans of the arguments and this is partly due to the hierarchical nature of dis- course relations. Finally, we discuss sense discrimination of the discourse connec- tives, which involves separating discourse connective from non-discourse connective senses and teasing apart the different dis- course connective senses, and discourse connective variation, the use of differ- ent connectives to represent the same dis- course relation. ∗I thank Aravind Johi and Martha Palmer for their com- ments. All errors are my own, of course. 1 Introduction The goal of the Chinese Discourse Treebank (CDTB) Project is to add a layer of discourse anno- tation to the Penn Chinese Treebank (Xue et al., To appear), the bulk of which has also been annotated with predicate-argument structures. This project is focused on discourse connectives, which include explicit connectives such as subordinate and coor- dinate conjunctions, discourse adverbials, as well as implicit discourse connectives that are inferable from neighboring sentences. Like the Penn English Discourse Treebank (Miltsakaki et al., 2004a; Milt- sakaki et al., 2004b), the CDTB project adopts the general idea presented in (Webber and Joshi, 1998; Webber et al., 1999; Webber et al., 2003) where discourse connectives are considered to be predi- cates that take abstract objects such as propositions, events and situations as their arguments. This ap- proach departs from the previous approaches to dis- course analysis such as the Rhetorical Structure The- ory (Mann and Thompson, 1988; Carlson et al., 2003) in that it does not start from a predefined in- ventory of abstract discourse relations. Instead, all discourse relations are lexically grounded and an- chored by a discourse connective. The discourse relations so defined can be structural or anaphoric. Structural discourse relations, generally anchored by subordinate and coordinate conjunctions, hold lo- cally between two adjacent units of discourse (such as clauses). In contrast, anaphoric discourse rela- tions are generally anchored by discourse adverbials and only one argument can be identified structurally in the local context while the other can only be de- 84 rived anaphorically in the previous discourse. An advantage of this approach to discourse analysis is that …

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