Different designers use different strategies to formulate a design problem. We introduce the Problem Map framework to study these differences, with formalized statements of formulation strategies. To formalize the strategies we define as set of operators in the Problem Map framework and represent formulation states. We have identified five tasks of problem formulation. For each task, we give an example of how a strategy can be traced in changes among states or in the sequence of the operators that were used to reach the resulting state. We also give examples of traces of three different strategies in protocols collected from eight experienced designers.