: Reasoning about knowledge seems to play a fundamental role in distributed systems. Indeed, such reasoning is a central part of the informal intuitive arguments used in the design of distributed protocols. Communication in a distributed system can be viewed as the act of transforming the system's state of knowledge. This paper presents a general framework for formalizing and reasoning about knowledge in distributed systems. We argue that states of knowledge of groups of processors are useful concepts for the design and analysis of distributed protocols. In particular, distributed knowledge corresponds to knowledge that is "distributed" among the members of the group, while common knowledge corresponds to a fact being "publicly known". The relationship between common knowledge and a variety of desirable actions in a distributed system is illustrated. Furthermore, it is shown that, formally speaking, in practical systems common knowledge cannot be attained. A number of weaker variants...

We discuss current approaches to the development of natural language dialogue systems, and claim that they do not sufficiently consider the unique qualities of man-machine interaction as distinct from general human discourse. We conclude that empirical studies of this unique communication situation is required for the development of user-friendly interactive systems. One way of achieving this is through the use of so-called Wizard of Oz studies. We describe our work in this area. The focus is on the practical execution of the studies and the methodological conclusions that we have drawn on the basis of our experience. While the focus is on natural language interfaces, the methods used and the conclusions drawn from the results obtained are of relevance also to other kinds of intelligent interfaces. 1 THE NEED FOR WIZARD OF OZ STUDIES Dialogue has been an active research area for quite some time in natural language processing. It is fair to say that researchers studying dialogue and di...

This paper re-assesses the role of real-time video as a technology to support interpersonal communications at distance. We review three distinct hypotheses about the role of video in the co-ordination of conversational content and process. For each hypothesis, we identify design implications and outstanding research questions derived from current findings. We first evaluate the non-verbal communication hypothesis, namely the prevailing assumption that the role of video is to supplement speech, and embodied in applications such as videoconferencing and videophone. We conclude that previous work has overestimated the importance of video at the expense of audio. This finding has strong implications for the implementation of such systems, and we make recommendations about both synchronisation and bandwidth allocation. Furthermore our own recent studies of workplace interactions point to other communicative functions of video. Current systems have neglected another potentially vital role of...

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this paper, I consider a range of English expressions and show that their context-dependency can be characterized in terms of two properties: 1. They specify entities in an evolving model of the discourse that the listener is constructing; 2. The particular entity specified depends on another entity in that part of the evolving "discourse model" that the listener is currently attending to

In conversation speakers design their utterances to be understood against the common ground they share with their addressees-their common experience, expertise, dialect, and culture. That ordinarily gives addressees an advantage over overhearers in understanding. Addressees have an additional advantage, we pro-pose, because they can actively collaborate with speakers in reaching the mutual belief that they have understood what was said, whereas overhearers cannot. As evidence for the proposal, we looked at triples of people in which one person told another person in conversation how to arrange 12 complex figures while an over-hearer tried to arrange them too. All three began as strangers with the same background information. As predicted, addressees were more accurate at arrang-ing the figures than overhearers even when the overhearers heard every word. Other evidence suggests that the very process of understanding is different for addressees and overhearers. 8 1989 Acadermc Press, Inc. People understand each other in conversations by gathering evidence about each other’s intentions. How do they do that? The traditional view, which we will call the autonom&s view, is that they listen to the words uttered, decode them, and interpret them against what they take to be the common ground of the participants in the conversation (e.g., Anderson,

In conversation, two people inevitably know different amounts about the topic of discussion, yet to make their references understood, they need to draw on knowledge and beliefs that they share. An expert and a novice talking with each other, therefore, must assess each other's expertise and accommodate to their differences. They do this in part, it is proposed, by assessing, supplying, and acquiring expertise as they collaborate in completing their references. In a study of this accommodation, pairs of people who were or were not familiar with New York City were asked to work together to arrange pictures of New York City landmarks by talking about them. They were able to assess each other's level of expertise almost immediately and to adjust their choice of proper names, descriptions, and perspectives accordingly. In doing so, experts supplied, and novices acquired, specialized knowledge that made referring more efficient. For success in conversation, people must continually appeal to their common ground—their mutual knowledge, beliefs, and

This paper presents a computational model of how conversational participants collaborate in making referring expressions. The model is based on the planning paradigm. It employs plans for constructing and recognizing referring expressions and meta-plans for constructing and recognizing clarifications. This allows the model to account for the generation and understanding both of referring expressions and of their clarifications in a uniform framework using a single knowledge base.

this paper as well as the competence and interests of its author. Rather, I shall look at just one feature: how subjects differ from nonsubjects in the text. More specifically, I shall investigate the differences between subjects and nonsubjects with respect to one formal phenomenon, definiteness, and one discourse phenomenon, the information-status of the entities that the subjects and nonsubjects represent.

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