Learning from past projects allows designers to avoid previous errors and to solve problems. Several methods have defined techniques to memorize lessons and experiences from projects in what we call project memory. This paper presents our traceability approach that allows to extract knowledge without perturbing designers' activities. Our approach is based on web technologies. In the one hand it keeps track of knowledge produced while using design tools (as a behavior model) , in the other hand, it restitutes knowledge according to a contextual situations recognition.