This article addresses issues related to traces modelling and visualisation in synchronous collaborative learning. The objective is to propose models and tools for representing, transforming, sharing and visualizing traces of users' experiences. The traces here represent the users' activities in their interactions with the learning platform. Our proposition is based on reflexive learning defined as the ability to interact with the situation, in order to meet one's own limitations. This work takes place in the ITHACA project which aims at developing an online learning platform that uses interaction traces as knowledge sources on, and for, the learners' learning as individuals or groups. In this paper, we propose a general framework for trace management and sharing, a generic model of synchronous collaborative activity based on the notion of interaction modes, which we specialized for whiteboard sharing and text chatting. We modelled an IRC client and developed a first implementation.