This paper concerns relationships among focus of attention, choice of referring expression, and perceived coherence of utterances within a discourse segment. It presents a framework and initial theory of centering intended to model the local component of attentional state. The paper examines interactions between local coherence and choice of referring expressions; it argues that differences in coherence correspond in part to the inference demands made by different types of referring expressions, given a particular attentional state. It demonstrates that the attentional state properties modeled by centering can account for these differences

This paper has three aims: (1) to generalize a computational account of the discourse process called CENTERING, (2) to apply this account to discourse processing in Japanese so that it can be used in computational systems for machine translation or language understanding, and (3) to provide some insights on the effect of syntactic factors in Japanese on discourse interpretation. We argue that while discourse interpretation is an inferential process, syntactic cues constrain this process, and demonstrate this argument with respect to the interpretation of ZEROS, unexpressed arguments of the verb, in Japanese. The syntactic cues in Japanese discourse that we investigate are the morphological markers for grammatical TOPIC, the postposition wa, as well as those for grammatical functions such as SUBJECT, ga, OBJECT, o and OBJECT2, ni. In addition, we investigate the role of speaker's EMPATHY, which is the viewpoint from which an event is described. This is syntactically indicated through the use of verbal compounding, i.e. the auxiliary use of verbs such as kureta, kita. Our results are based on a survey of native speakers of their interpretation of short discourses, consisting of minimal pairs, varied by one of the above factors. We demonstrate that these syntactic cues do indeed affect the interpretation of ZEROS, but that having previously been the TOPIC and being realized as a ZERO also contributes to the salience of a discourse entity. We propose a discourse rule of ZERO TOPIC ASSIGNMENT, and show that CENTERING provides constraints on when a ZERO can be interpreted as the ZERO TOPIC

Based on empirical evidence from a free word order language (German) we propose a fundamental revision of the principles guiding the ordering of discourse entities in the forward-looking centers within the centering model. We claim that grammatical role criteria should be replaced by indicators of the functional information structure of the utterances, i.e., the distinction between context-bound and unbound discourse elements. This claim is backed up by an empirical evaluation of functional centering.

Centering Theory is the best known framework for theorizing about local coherence and salience; however, its claims are articulated in terms of notions which are only partially specified, such as ‘utterance’, ‘realization’, or ‘ranking’. A great deal of research has attempted to arrive at more detailed specifications of these PARAMETERS of the theory; as a result, the claims of Centering can be INSTANTIATED in many different ways. We investigated in a systematic fashion the effect of these different ways of setting the parameters on the theory’s claims. Doing this required, first of all, to clarify what the theory’s claims are (one of our conclusions being that what has become known as ’Constraint 1 ’ is actually a central claim of the theory). Secondly, we had to clearly identify these parametric aspects: e.g., we argue that the notion of ‘pronoun ’ used in Rule 1 should be considered a parameter. Thirdly, we had to find appropriate methods for evaluating these claims. We found that while the theory’s main claim about salience and pronominalization, Rule 1–a preference for pronominalizing the CB–is verified with most instantiations, Constraint 1–a claim about (entity) coherence and CB uniqueness–is much more instantiation-dependent: it is not verified if the parameters are instantiated according to very mainstream views (‘Vanilla instantiation’), it only holds if indirect realization is allowed, and is violated by between 20

The definitions of the basic concepts, rules, and constraints of centering theory involve underspecified notions such as ‘previous utterance’, ‘realization’, and ‘ranking’. We attempted to find the best way of defining each such notion among those that can be annotated reliably, and using a corpus of texts in two domains of practical interest. Our main result is that trying to reduce the number of utterances without a backwardlooking center (CB) results in an increased number of cases in which some discourse entity, but not the CB, gets pronominalized, and viceversa. 1

this paper we follow the version that was rst implemented in the algorithm by Brennan et al. (1987) and is more clearly stated in Walker et al. (1998a). Under this interpretation the Cb(Un) can be unde ned

The goal of this paper is to examine the relationship between Centering transitions (Grosz et al., 1995) and choice of referring expression. For that purpose, Centering analyses were carried out in two different corpora of spoken Spanish. The corpus analysis confirms reports in previous literature about what is the typical choice of referring expression. In some cases, however, the referring expression chosen violates expectation, or does not follow what other researchers have found (e.g., a proper name is used when a pronoun is expected). In those cases, the most likely explanation is that other constraints related to spoken language are at play (turn-taking and grounding). 1.

Contents 1 Introduction 1 2 Issues in Anaphora Resolution 2 2.1 Recency and Search Space . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.2 Contra-Indexing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.3 Agreement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.4 Stressing of Pronouns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.5 Cataphora . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.6 Set Generation and Plurals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.7 Generic 'It' and 'They' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.8 Semantic Reasoning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.9 Speaker's and Semantic Referent . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.10 Parallelism . . . . . . . . . . . . . . . .

This paper describes an application of Centering Theory (Grosz et al. 1995) to dialogue in Spanish. Centering is a theory of local focus and local discourse coherence. It also relates focus in discourse to choice of referring expression.

In this thesis, within the framework provided by the Construction-Integration (CI) model of comprehension, we investigate the topicality of referents in discourse in terms of the activations of the memory elements corresponding to those referents. We discovered the inherent deficiencies of the CI model in displaying the linguistic observations about how dierent syntactic cues relate to sentence-level topic. This thesis proposes enhancements to the CI model so that it incorporates and makes use of the two sources of grammatical information prevalent for topicality at the sentence-level: the grammatical role of the participants and the clausal organization of sentences. Computational tests are carried out to compare the original and the modified CI models. The comparisons have shown that the modified CI model is more successful at identifying the topic of single sentences. We have also implemented two aspects of discourse-level topic, i.e. topic shifts and referential continuity, in the modified CI model.