During the realization of a document-mediated collective task the participants act and interact by creating documents and ontologies, by modifying them, annotating them and exchanging them. This article presents the general principles of a model based on a multi-agent architecture, aimed at facilitating the co-construction of common ontologies. The model is built on the MUSETTE (Modelling USEs and Tasks for Tracing Experience) approach, which was designed to provide users with assistance based on the recording and reusing of their system use traces. Our model, called MAZETTE (Multi-Agent MUSETTE), defines a framework for considering sharing and reusing of collective traces and experience, amongst which we focus on ontology co-construction and reuse.