The negotiation model. The negotiation model in C-CHENE is embedded in the design of the communication interface (lower part of Figure 2). The lower part of the communication area contains a set of buttons to be used by both students for performing
different communicative acts, and the upper part the ongoing interaction history displayed for the students. The interaction history is an important resource in collaborative dialogue since it provides a common objective reference to previous activity (unlike oral dialogues) that encourage reflection and effective collaboration [Collins & Brown, 1988; Katz & Lesgold 1993].
The first rationale for designing the new button-based interface was to ease the students' typing load, thus freeing up time for more problem-solving task related discussion. The second was to encourage the students to engage in certain pedagogically preferred communicative activities (e.g. using the "Because" button to give reasons and explanations for intermediary solutions). This hypothesis was confirmed by analysis of transcripts of six pairs of students using the new interface. The third was to avoid some natural language interpretation problems (e.g. illocutionary force recognition), thus facilitating dialogue and belief modelling.
The set of CA buttons provided was designed on the basis of analysis of a corpus of 'chat-box'
interactions with C-CHENE, and existing models for information dialogues [Moeschler, 85; Bunt, 89, 95] or collaborative problem-solving interactions [Baker, 94].