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Human-like characters in the interface may evoke social responses in users, and literature suggests that realism is the most important factor herein. However, the effects of interface characters on the user are not well understood. We developed an integrative framework, called I-PEFiC, to explain 'persona' and realism effects on the user. We tested an important part of the model using an experimental design in which 140 middle school students were class-wise shown an informative virtual reality demonstration that incorporated either a realistic or an unrealistic (fantasy) interface character, or no character. Findings show, first, no persona effect on task performance. We discuss how user engagement might be related to persona effects. Second, designed realism of the interface character contributed to user engagement when controlled for various user perceptions. Moreover, perceived aesthetics and task-relevance further influenced user engagement. Third, user engagement and task performance combined better predicted satisfaction than either one of the factors alone. In sum, several appearance-and task-related factors contributed to user engagement and user satisfaction. Thus, realism is not all.

Abstract.Many different task modeling methods exist. In this paper, we discuss 1) ingredients common to most task models, 2) how task modeling relates to the design of user interfaces, and 3) our proposed ontology for task analysis. We then show our task analysis tool that is based on the ontology. It is our belief that task models should be based on an ontology that describes the relevant concepts and the relationships between them, independently of any used graphical representations. Such an ontology helps to understand the different task modeling methods and it can also be operationalized for use in tools.

Summary. In this chapter we propose a scripting language, called STEP, for embodied agents, in particular for their communicative acts like gestures and postures. Based on the formal semantics of dynamic logic, STEP has a solid semantic foundation, in spite of a rich number of variants of the compositional operators and interaction facilities on worlds. STEP has been implemented in the distributed logic programming language DLP, a tool for the implementation of 3D web agents. In this chapter, we discuss principles of scripting language design for embodied agents and several aspects of the application of STEP.

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