  This article presents the Cogni-CISMeF project, which aims at improving the
health information search engine CISMeF, by including a conversational agent
that interacts with the user in natural language. To study the cognitive
processes involved during information search, a bottom-up methodology was
adopted. An experiment has been set up to obtain human dialogs related to such
searches. The analysis of these dialogs underlines the establishment of a
common ground and accommodation effects to the user. A model of artificial
agent is proposed, that guides the user by proposing examples, assistance and
choices.
