Abstract: Collaborative designs generally result in artefacts' solutions which are enriched by the multiple expertise and skills of the designers engaged in the design task. However, because designers have their own knowledge, expertise and insight, reaching a shared point of view from multiple and not necessarily coherent ones is difficult and often leads to conflicts during the design stage. To address this problem, we describe a new methodology for modelling the conflict management process and its implementation in a Web-based multi-agent system for advanced concurrent design and manufacturing with emphasize on the concept of “cognitive synchronisation” and “design rational” for building a shared point of view and thus reaching a “satisfying” solution.