A Two-Level Approach To Coding Dialogue For Discourse Structure: Activities Of The 1998 DRI Working Group On Higher-Level Structures

This paper presents a novel two-level scheme for coding discourse structure in dialogue, which was created by the authors for the discourse structure subgroup of the 1998 DR/meet ing on dialogue tagging. We discuss the theoretical motivations and framework for the coding proposal, and then review the results of coding exercises performed by the 1998 DR/ discourse structure subgroup using the new manual. Finally, we provide suggestions for improving the scheme arising from the working group activities at the third DRI meeting. 1 I n t r o d u c t i o n A two-level scheme for coding discourse structure in dialogue has been proposed and undergone initial testing within the DR/effort . In particular, the higher-level structures working group of the third DR/ was charged with the task of creating a coding scheme concerned exclusively with the discourse structure of dialogue. Finding a good starting point The discourse structure working group was chaired by Christine Nakatani (Bell Laboratories, Lucent Technologies) and co-chaired by David Traum (U Maryland). Pre-meeting group participants also included Jean Carletta (U Edinburgh), Jennifer Chu-Carroll (Bell Laboratories, Lucent Technologies), Peter I-Iceman (Oregon Graduate Institute), Juha Hirschberg (AT&T Labs), Masato Ishizaki (JAIST), Diane Litman (AT&T Labs), Owen Rainbow (Cogentex), Jennifer Venditti (Ohio State U), Marilyn Walker (At&T Labs), Gregory Ward (Northwestern U). Participants at the meeting also included Ellen Bard (U Edinburgh), Yasuo Horiuchi (Chiba U), Koichi Hoshida (ATR), Yasuhiro Katagisi (NTT), Kikuo Maekawa (NLRI), Michael Strube (U Pennsylvania), Masafumi Tamato (NTT), Yuki Tateishi (Tokyo U), and Takahiro Wakao (TAO). for a consensus coding scheme for discourse structure in dialogue was a non-trivial task. Most discourse structure schemes in fact were geared toward monologue, and most dialogue coding schemes omitted the higher-level structures that were essential to the monologue schemes, or provided only genre or domain-specific higher-level structures. Given the limited amount of work in this area, it was impossible to at tempt a comprehensive coding scheme for all aspects of discourse structure ill dialogue. Instead, we were guided by an analysis of what choices needed to be made in creating a coding scheme. (Traum, 1998) identifies three dimensions along which discourse structure schemes can be classifted: granularity, content, s t ruc tur ing mechanisms. • Granulari ty: how much material (time, text, turns, etc.) is covered by the units (minimum, maximum, and average)? Granularity ranges were divided roughly into three categories: M i c r o roughly within a single turn M e s o roughly an exchange, IR-unit, "game", or short "sub-dialogue", M a c r o coherent larger spans, related to overall dialogue purposes. • Content: what is this a structure of(e.g., intentions, accessibility, effects, etc.)? • • S t ruc tur ing mechanisms: What kinds of units and structuring principles are used (e.g., fiat, set inclusion, hierarchical/CFG structuring, relational)? How many primitive types of units are allowed (one basic unit type, two or three types of units, or several types)? This multi-dimensional space was then used to classify different extant coding schemes as to which aspects they are concerned with. Guided by this principled survey of various schemes, we decided on an objective of defining a