In dynamic working environments such as factory production lines, the process of decision-making combines different types of data and knowledge available in different forms. In many cases, elements impacting decisions are not totally mastered by the decision support system since the activity of the user is highly influenced by the dynamic change of the production system. Thus, in order to set the appropriate context elements surrounding different working situations of factory actors, this paper proposes a context model aiming to represents user’s activity and the circumstances under the decision-making process. The literature of related works highlighted the advantages of context-awareness in supporting the dynamic adaptation of information according to user’s context. The proposed model in this paper takes advantage from the context notion and the fundaments of the activity theory proposed in cognitive science. The intended model is used in an intelligent assistant system dedicated to assist factory workers in the manufacturing process. The main purpose of the context model is to help the assistant system in handling the process of knowledge adaptation and therefore, avoiding the problems of overload and misinterpretation of the information.