Attribution and the (Non-)Alignment of Syntactic and Discourse Arguments of Connectives

Proceedings of the Workshop on Frontiers in Corpus Annotation II: Pie in the Sky, pages 29–36, Ann Arbor, June 2005. c⃝2005 Association for Computational Linguistics Attribution and the (Non-)Alignment of Syntactic and Discourse Arguments of Connectives Nikhil Dinesh and Alan Lee and Eleni Miltsakaki and Rashmi Prasad and Aravind Joshi University of Pennsylvania Philadelphia, PA 19104 USA fnikhild,aleewk,elenimi,rjprasad,joshi g@linc.cis.upenn.edu Bonnie Webber University of Edinburgh Edinburgh, EH8 9LW Scotland bonnie@inf.ed.ac.uk Abstract The annotations of the Penn Discourse Treebank (PDTB) include (1) discourse connectives and their arguments, and (2) attribution of each argument of each con- nective and of the relation it denotes. Be- cause the PDTB covers the same text as the Penn TreeBank WSJ corpus, syntac- tic and discourse annotation can be com- pared. This has revealed significant dif- ferences between syntactic structure and discourse structure, in terms of the argu- ments of connectives, due in large part to attribution. We describe these differences, an algorithm for detecting them, and fi- nally some experimental results. These re- sults have implications for automating dis- course annotation based on syntactic an- notation. 1 Introduction The overall goal of the Penn Discourse Treebank (PDTB) is to annotate the million word WSJ cor- pus in the Penn TreeBank (Marcus et al., 1993) with a layer of discourse annotations. A preliminary re- port on this project was presented at the 2004 work- shop on Frontiers in Corpus Annotation (Miltsakaki et al., 2004a), where we described our annotation of discourse connectives (both explicit and implicit) along with their (clausal) arguments. Further work done since then includes the an- notation of attribution: that is, who has expressed each argument to a discourse connective (the writer or some other speaker or author) and who has ex- pressed the discourse relation itself. These ascrip- tions need not be the same. Of particular interest is the fact that attribution may or may not play a role in the relation established by a connective. This may lead to a lack of congruence between arguments at the syntactic and the discourse levels. The issue of congruence is of interest both from the perspective of annotation (where it means that, even within a single sentence, one cannot merely transfer the an- notation of syntactic arguments of a subordinate or coordinate conjunction to its discourse arguments), and from the perspective of inferences that these an- notations will support in future applications of the PDTB. The paper is organized as follows. We give a brief overview of the annotation of connectives and their arguments in the PDTB in Section 2. In Section 3, we describe the annotation of the attribution of the arguments of a connective and the relation it con- veys. In Sections 4 and 5, we describe mismatches that arise between the discourse arguments of a con- nective and the syntactic annotation as provided by the Penn TreeBank (PTB), in the cases where all the arguments of the connective are in the same sen- tence. In Section 6, we will discuss some implica- …

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