4.1 Grounding mechanisms are use to built shared sub-spaces

4.1.1 Grounding facts from the task

Two types of domain knowledge must be shared: facts directly accessible from interactions with objects or suspects (E.g. "Rolf Loretan was in the bar at 8 pm") and inferences drawn by detectives (e.g. "Hans could not get the gun"). We talk here about the former, discussing the latter in the next section. These facts are persistent: any information true at some time will remain true during the whole task. When detectives visit rooms separately, they have good reason to think that the information is not accessible to their partner. Hence, they generally make this information accessible (level 1 of sharedness) by putting a note on the whiteboard or by telling directly through MOO discussions. Since the whiteboard is not scrollable, they know that any information put there should be perceived by their partner (level 2 of sharedness). Many of these facts are important to reach the solution, but the detectives do not know in advance which ones will be important. However, what seems to require agreement (level 4) is not the fact itself, but its importance in the story. The grounding mechanism will differ according to the subjective importance given by this fact: simple facts are just put on the whiteboard (example 1), while supposedly important facts are communicated directly (example 2) or indirectly (example 3). When doubts exist regarding whether an important fact was accessible to the partner (level 2), it is explicitly grounded before (example 4) or verified afterwards (example 5).

Both detectives have notebooks which record all answers to the questions they asked to suspects. This notebook was functionally redundant with the whiteboard, as an 'individual memory support'. Pair 7 do not use notebooks but use the whiteboard as a notebook. In addition, these notebooks could also useful as a 'shared memory support'. We initially provided a command for merging the content of these notebooks ('compare'): Each detective had hence access to all the facts collected by his partner. Pair 4 uses this command 7 times. Quite logically, they don't use the whiteboard to report these facts, but rather to organize them. In later experiments we suppressed this command in order to give the whiteboard its full role. However, two out of the three remaining pairs developed a functionally equivalent mechanism: pair 5 simply exchanged their notebooks, while in pair 6 Hercule reads his notebook to Sherlock (see (example 27)example 27).

Grounding in Multi-modal Task-Oriented Collaboration - 3 SEP 1996
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