The recent success of various Apple products affirms that usability engineering can be a beneficial asset in software product development. But considerable problems exist in integrating usability engineering and software engineering. In this paper, we argue that the technical basis - the disciplines' artifacts and used tools - are a potential hurdle for integration. Model-driven development (MDD) is put forward to address these problems. The Mapache approach persued in our research specializes MDD for User Interface (UI) engineering. Four of its concepts are discussed in the light of integrating usability and software engineering.