We discuss the need for a robust model interchange document format in order to realize the Model Driven Engineering vision. The OMG proposes XMI and XMI[DI] as the standard document formats to store and exchange models and diagrams between applications. However, there are still some open issues regarding the current version of these standards. In this article, we discuss some of these issues and conclude with a plea for a continued discussion on the future and improvement of the XMI and the XMI[DI] model interchange standards.