Direct Inquiry and Research. A model should help to direct inquiry and research into public policy. A concept should be operational - that is, it should refer directly to real -world phenomena that can be observed, measured,and verified. A concept,or a series of interrelated concepts (which we refer to as a model ), should suggest relationships in the real world that can be tested and verified. If there is no way to prove or disprove the ideas suggested by a concept,the concept is not really useful in developing a science of politics.