ParseTalk about Sentence- and Text-Level Anaphora

ParseTalk about Sentence- and Text-Level Anaphora Michael Strube and Udo Hahn C~Z~- Computational Linguistics Research Group Freiburg University D-79085 Freiburg, Germany {strube, hahn}@coling.uni-freiburg.de Abstract We provide a unified account of sentence-level and text-level anaphora within the framework of a dependency-based grammar model. Criteria for anaphora resolution within sentence boundaries rephrase major concepts from GB's binding theory, while those for text-level anaphora incorporate an adapted version of a Grosz-Sidner-style focus model. 1 Introduction This paper treats the resolution of anaphora with- in the framework of Parse Talk, a dependency- oriented grammar model that incorporates strict lexicalization, head-orientation (based on valency specifications), feature unification, and inheri- tance among lexicalized grammar specifications (Br6ker et al., 1994; Hahn et al., 1994). The re- sults we present rest upon two major assumptions: 1. As many forms of anaphors (e.g., nomi- nal and pronominal anaphors) occur within sentence boundaries (so-called intra-sentential or sentence anaphora) and beyond (inter- sentential or text anaphora), adequate theo- ries of anaphora should allow the formulation of grammatical regularities for both types us- ing a common set of grammatical primitives. 2. Anaphora are only one, yet very prominent phenomenon that yields textual cohesion in discourse. Adequate grammars should there- fore also be easily extensible to cover non- anaphoric text phenomena (e.g., coherence re- lations, rhetorical predicates), which provide for additional levels of text (macro) structure, with descriptions stated at the same level of theoretical sophistication as for anaphora. First, we will briefly compare our approach with work done in the context of government-binding (GB) grammar and discourse representation the: ory (DRT). As we conceive it, binding theory as developed within the GB framework (Chomsky, 1981; Kuno, 1987) offers one of the most sophis- ticated approaches for treating anaphora at the sentence level of description. This has also been recognized by advocates of competing grammar formalisms, who have elaborated on GB's bind- ing principles (cf., e.g., Pollard and Sag (1992) within the context of HPSG, whose treatment is nevertheless restricted to reflexive pronouns). In- terestingly enough, when faced with some cru- cial linguistic phenomena, such as topicalization, GB must assume rather complex movement oper- ations in order to cope with the data in a satisfac- tory manner. Things get even more complicated when languages with relatively free word order, such as German, are taken into account. Finally, considering the case of text anaphora, binding the- ory has nothing to offer at all. Another strong alternative for considering ana- phora constitutes the framework of DRT (Kamp and Reyle, 1993). Its development can be con- sidered a landmark in the model-theoretic se- mantic analysis of various forms of quantified sentences, conditionals, and anaphorically linked multi-sentential discourse. At this level of descrip- tion, DRT is clearly superior to GB. On the other hand, its lack of an equally thorough treatment of complex syntactic constructions makes it inferior to GB. These deficits are no wonder, since DRT is not committed to any particular syntactic theory, and thus cannot place strict enough syntactic con- straints on the admissible …

Content truncated to 500 words