[Dillenbourg and Traum, 1999] Dillenbourg, P. and Traum, D. (1999). Does a shared screen make a shared solution? In Hoadly, C. and Roschelle, J., editors, Proceedings of the Third Conference on Computer Supported Collaborative Learning, pages 127–135, California: Stanford University. Available from: http://www.ict.usc.edu/~traum/Papers/cscwHTML/cscl99-dil&traum2.html.
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The main concept contained in this paper is that the term ‘shared understanding’ is used inconsistently at linguistic level and at cognitive level. In the first case, the term is concentrated with the understanding of a sentence. In the second case, it is concerned with the understanding of a problem and its solution or even with the understanding of a domain. The authors stated that it is hard to find a relationship between the cognitive and the linguistic level, namely to describe how grounding mechanism contribute to build a shared solution.

Therefore their approach was to describe how grounding mechanism vary according to task criteria. The ‘grounding criterion’ is, for them a syntetic account of various parameters, such as the probability of non-grounding (high for ambiguos or polemical messages), the cost of non-grounding (how detrimental it is to misunderstand) and persistency of information.

The first question they try to answer is wether a shared witheboard contribute to grounding utteraces. They proved that witheboard was used to fix a shared representation of the ongoing problem solving, wether the dialogues in the chat was used to ground witheboard information.

In this study they assimilated grounding intensity with the rate of acknowledgment. And, to this extent, the rate of acknowledgment is not related to the global performance measure.

Two last comments: (1) I feel that a possible link between the grounding at utterance level and grounding at a cognitive level may be represented by the introduction of markers that look at perspective taking and mutual modelling; (2) I dout the assimilation of grounding intensity with the rate of acknowledgment for the same extent that acknowledgment in not a direct reflection of grounding. I might acknowledge an utterance for the sake of continuing the conversation without a real comprehension of the emitter comunicative intent. Can we use here different markers, like actions which might reflect more to what the person understood? (3) I like the idea that we can assimilate understanding, misunderstanding and disagreement for the purpose of learning: both activates a situation (sometimes conflictual) which can support negotiation and therefore mutual understanding (Blaye, 1988).