We discuss external and internal graphical and linguistic representational systems. We argue that a cognitive theory of peoples' reasoning performance must account for (a) the logical equivalence of inferences expressed in graphical and linguistic form; and (b) the implementational differences that affect facility of inference. Our theory proposes that graphical representations limit abstraction and thereby aid processibility. We discuss the ideas of specificity and abstraction, and their cognitive relevance. Empirical support comes from tasks involving (i) the manipulation of external graphics; and (ii) no external graphics. For (i), we take Euler's Circles, provide a novel computational reconstruction, show how it captures abstractions, and contrast it with earlier construals, and with Mental Models' representations. We demonstrate equivalence of the graphical Euler system, and the non-graphical Mental Models system. For (ii), we discuss text comprehension, and the mental ...

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To explain complex phenomena, an explanation system must be able to select information from a formal representation of domain knowledge, organize the selected information into multisentential discourse plans, and realize the discourse plans in text. Although recent years have witnessed significant progress in the development of sophisticated computational mechanisms for explanation, empirical results have been limited. This paper reports on a seven-year effort to empirically study explanation generation from semantically rich, large-scale knowledge bases. In particular, it describes KNIGHT, a robust explanation system that constructs multisentential and multiparagraph explanations from the Biology Knowledge Base, a large-scale knowledge base in the domain of botanical anatomy, physiology, and development. We introduce the Two-Panel evaluation methodology and describe how KNIGHT'S performance was assessed with this methodology in the most extensive empirical evaluation conducted on an explanation system. In this evaluation, KNIGHT scored within "half a grade " of domain experts, and its performance exceeded that of one of the domain experts. 1.

Multilingual instructions generation has been the object of many studies recently, motivated by the increased need to produce multilingual manuals coupled with the cost of technical writing and translating. These studies concentrate on the automatic generation of instructions, leaving technical writers out of the loop. In many cases, however, it is not possible to dispense with human intervention entirely, for at least two reasons. First, the system must be provided with a semantic knowledge base from which the instructions can be generated. Second, it is the technical writers who have the expertise necessary for producing instructions appropriate for a specific product or company, and it is not necessarily an easy task to make this expertise available to a system. The results of a requirement analysis study confirm the view that the most useful tool is not a stand-alone writing tool but rather one that supports technical writers in their task. In this paper, we describe such a support tool, which we developed based on the results of our user requirement analysis.

This paper introduces the special issue of Knowledge-Based Systems on HumanComputer Collaboration (HCC). It derives a set of fundamental issues from a definition of collaboration, introduces two major approaches to HCC, and surveys each approach, showing how it formulates and addresses the issues. It concludes by proposing some themes that should characterize a unified approach to human-computer collaboration. 1 Introduction Collaboration is a process in which two or more agents work together to achieve shared goals. Thirty researchers came together in Raleigh, North Carolina in October of 1993 for a AAAI Fall Symposium dedicated to this topic. The goal of the symposium was to achieve a better understanding of Human-Computer Collaboration (HCC), collaboration involving at least one human and one computational agent. In particular, the symposium sought to explore the fundamental nature of collaborative problem solving, understand the constraints brought to bear by the differing charac...

Lifelike animated agents for knowledge-based learning environments can provide timely, cus-tomized advice to support students ' problem solving. Because of their strong visual presence, they hold signi cant promise for substantially increasing students ' enjoyment of their learning experiences. Akey problem posed by lifelike agents that inhabit arti cial worlds is deictic believability. In the same manner that humans refer to objects in their environment through judicious combinations of speech, locomotion, and gesture, animated agents should be able to move through their environment, and point to and refer to objects appropriately as they provide problem-solving advice. In this paper we describe a framework for achieving deictic believabil-ity in animated agents. A deictic behavior planner exploits a world model and the evolving explanation plan as it selects and coordinates locomotive, gestural, and speech behaviors. The resulting behaviors and utterances are believable, and the references exhibit a lack ofambiguity. This approach to spatial deixis has been implemented in a lifelike animated agent, Cosmo, who inhabits a learning environment for the domain of Internet packet routing. Cosmo provides realtime advice to students as they escort packets through a virtual world of interconnected routers. Results of an informal focus group study with the Cosmo agent suggest that the spatial deixis framework produces clear explanatory animated behaviors. 1 1

Natural-language generation (NLG) techniques can be used to automatically produce technical documentation from a domain knowledge base and linguistic and contextual models. We discuss this application of NLG technology from both a technical and a usefulness (costs and benefits) perspective. This discussion is based largely on our experiences with the idas documentation-generation project, and the reactions various interested people from industry have had to idas. We hope that this summary of our experiences with idas and the lessons we have learned from it will be beneficial for other researchers who wish to build technical-documentation generation systems.

One of the most promising opportunities in-troduced by rapid advances in knowledge-based learning environments and multimedia technolo-gies is the possibility of creating animated peda-gogical agents. These agents should exhibit three properties: timely domain coverage (they should clearly communicate fundamental concepts and relationships within the allotted time); contextu-ality (they should provide explanations in appro-priate problem-solving contexts); and continuity (their activities and utterances should be peda-gogically, visually, and aurally coherent). We have developed the coherence-structured be-havior space approach to creating animated ped-agogical agents. This is a two-step approach. First, we design a behavior space of anima-tion and audio segments that are structured by prerequisite relationships and a continuity metric. Second, we navigate coherent paths through the space to dynamically sequence be-haviors. This creates seamless global behav-iors that communicate fundamental knowledge and provide contextualized problem-solving ad-vice. The coherence-structured behavior space approach has been implemented in Herman the Bug, an animated pedagogical agent for Design-A-Plant, a knowledge-based learning environ-ment for botanical anatomy and physiology. For-mative evaluations of the agent with middle school students are encouraging.

The task of the knowledge-based presentation system WIP is the generation of a variety of multimodal documents from an input consisting of a formal description of the communicative intent of a planned presentation. WIP generates illustrated texts that are customized for the intended audience and situation. We present the architecture of WIP and introduce as its major components the presentation planner, the layout manager, the text generator and the graphics generator. An extended notion of coherence for multimodal documents is introduced that can be used to constrain the presentation planning process. The paper focuses on the coordination of contents planning and layout that is necessary to produce a coherent illustrated text. In particular, we discuss layout revisions after contents planning and the influence of layout constraints on text generation. We show that in WIP the design of a multimodal document is viewed as a non-monotonic planning process that includes various revisions of preliminary results in order to achieve a coherent output with an optimal media mix. 1

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