We need non-formal methods based on formal models in interaction design

With collaborative interaction design, formal models have to be used by expert stakeholders in order to work effectively and efficiently. But these formal models should not be discussed with non-expert stakeholders. Therefore, we use non-formal methods which are based on our formal models when we talk to non-expert stakeholders. Without having formal models in mind, non-formal methods cannot be applied effectively for a collaborative design of interactions. Non-formal methods like an open requirements elicitation in form of workshops or interviews may fail gaining all necessary information if there is no formal model which builds the basis for the non-formal methods. Only with formal models, we are able to plan, lead, and analyze non-formal methods in a way to get optimal results.