this paper, we focus on two levels of analysis. The first involves the relation between the information conveyed in consecutive elements of a coherent discourse. Thus, for example, one utterance may describe an event that can be presumed to be the cause of another event described in the subsequent utterance. This causal relation is at what we will call the informational level. The second level of relation results from the fact that discourses are produced to effect changes in the mental state of the discourse participants. In coherent discourse, a speaker is carrying out a consistent plan to achieve the intended changes, and consecutive discourse elements are related to one another by means of the ways in which they participate in that plan. Thus, one utterance may be intended to increase the likelihood that the hearer will come to * Department of Computer Science and Intelligent Systems Program, University of Pittsburgh, Pittsburgh, PA 15260. e-mail: jmoore,pollackcs.pitt.edu 1 In addition, intentional structure is needed to make certain types of choices during the generation process, e.g., how to refer to an object (Appelt 1985)

The notion that a text is coherent in virtue of the `relations' that hold between its component spans currently forms the basis for an active research programme in discourse linguistics. Coherence relations feature prominently in many theories of discourse structure, and have recently been used with considerable success in text generation systems. However, while the concept of coherence relations is now common currency for discourse theorists, there remains much confusion about them, and no standard set of relations has yet emerged. The aim of this thesis is to contribute towards the development of a standard set of relations. We begin from an explicitly empirical conception of relations: they are taken to model a collection of psychological mechanisms operative during the tasks of reading and writing. This conception is fleshed out with reference to psychological theories of skilled task performance, and to Rosch's notion of the basic level of categorisation. A methodology for investi...

This paper presents an analysis of purpose clauses in the context of instruction understanding. Such analysis shows that goals affect the interpretation and / or execution of actions, lends support to the proposal of using generation and enablement to model relations between actions, and sheds light on some inference processes necessary to interpret purpose clauses.

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INTRODUCTION Given the prevalence of the use of rhetorical rela- tions in the generation of text (Hovy, 1989; Moore and Paris, 1988; Scott and Souza, 1990), it is surprising how little work has actually been done on the grammatical realization of these relations. Most systems, based on Mann and Thompson's formulation of Rhetorical Structure Theory (Mann and Thompson, 1988), have adopted simplified so- lutions to their expression. If, for example, an action, X, and a purpose for that action, Y, must be expressed, a standard form such as "Do X in order to Y" will be generated. In reality, the purpose relation can be and is expressed in a myriad of different ways depending upon numerous functional considerations. Consider the following examples: (la) Follow the steps in the illustration below, for desk installation. (code ) (lb) To install the phone on a desk, follow the steps in the illustration below. (lc) Follow the step.s in the illustration below, for installing the phone on a

The notion that a text is coherent in virtue of the `relations' which hold between the elements of that text has become fairly common currency, both in the study of discourse coherence and in the field of text generation. The set of relations proposed in Rhetorical Structure Theory (Mann and Thompson [14]) has had particular influence in both of these fields. But the widespread adoption of `relational' terminology belies a certain amount of confusion about the relational constructs themselves: no two theorists use exactly the same set of relations; and often there seems no motivation for introducing a new relation beyond considerations of descriptive adequacy or engineering expedience. To alleviate this confusion, it is useful to think of relations not just as constructs with descriptive or operational utility, but as constructs with psychological reality, modelling real cognitive processes in readers and writers. This conception of rhetorical relations suggests a methodology for delin...

This paper discusses an approach to planning the content of instructional texts. The research is based on a corpus study of 15 French procedural texts ranging from step-by-step device manuals to general artistic procedures. The approach taken starts from an AI task planner building a task representation, from which semantic carriers are selected. The most appropriate RST relations to communicate these carriers are then chosen according to heuristics developed during the corpus analysis.

A great part of the product knowledge in manufacturing enterprises is only available in the form of natural language documents. The know-how recorded in these documents is an essential resource for successful competition in the market. From the viewpoint of knowledge management, however, documents have a severe limitation: They do not capture the wealth of knowledge contained in these documents, since the entire knowledge is not spelled out on the linguistic surface. In order to overcome this limitation, the notion of a document as a particular kind of realization of (or view on) the underlying knowledge is introduced. The paper discusses the major steps in realizing this approach to documents: Knowledge acquisition, knowledge representation, and techniques to automatically generate multilingual documents from knowledge bases. Further, the paper describes how the required product knowledge can be represented in a sharable and reusable way.

An active research programme in Natural Language Generation has grown up around the notion of `coherence relations'. Relations are being used in a variety of roles in generation systems, in planning the structure of messages and in guiding their linguistic realisation. However, a confusing diversity exists between systems with respect to the particular relations they use.

An approach to the computational treatment of style is presented in the case of generation of informative texts. We regard the style moztly as a means of controlled selection of lternatives faced at each level of text generation. The generation technique, as we]] as the style specification, are considered at four levels -- content production, discourse generation surface structure development, and lexical choice. A style is specified by the frequency of occurrence of certain features examined through observation of particular texts. The algorithm for text generation ensures efficient treatment of the style requirements.