There is a common trend towards Graphical User Interfaces (GUI). Writing applications for such an environment puts new demands on designing software and managing its development. The applications software needs to be event based. It needs to have a special uniform "feel" and provide flexibility for both the novice and experienced user.Many of the new GUI oriented needs can be handled by traditional User Interface Toolkits or Libraries. However, using these will not solve the complexity of a good user interface design. Another approach is to choose or design a User Interface Management System (UIMS). UIMS is responsible for all user interface action and only when necessary will call actual application code for performing e.g. a calculation or data base operation.The paper describes the architecture of a large real-life UIMS based APL application project. Since a UIMS approach differs from traditional hierarchical programming, many of these differences are described in detail. Particular emphasis has been put on how this approach has affected project management and the various tasks of a software project. The paper ends by presenting some thoughts about future APL Application Development Systems.