The adaptation of Product/Service-System calls for new development models. On one side this businesses give the manufacturing firm possibilities to redesign, upgrade and replace the discrete device that provides the performance their customers are asking for. On the other side, this new situation has to address aspects that are normally not addressed in early product development, i.e., services. In this chapter, we will elaborate on product and service development processes models, as well as system models to propose a frame of reference for multiple perspectives on PSS development. These perspectives are people, product and process. Also, this chapter puts forward implications for the development of PSS models.