Making Applications in KSWorld

We report on our experiences in creating a GUI framework called KSWorld, which supports an interactive and declarative manner of application writing. The framework embodies direct manipulation, a high degree of loose coupling, and time-aware execution derived from Functional Reactive Programming (FRP). We also describe how a universal document editor was developed in this framework. The fields, or slots, of graphical widgets in KSWorld are reactive variables. Definitions of such variables can be added or modified in a localized manner, allowing on-the-fly customization of the visual and behavioral aspects of widgets and entire applications. Thus the KSWorld environment supports highly exploratory application building: a user constructs the appearance interactively with direct manipulation, then attaches and refines reactive-variable definitions to achieve the desired overall behavior. We also show that the system scales up sufficiently to support a universal document editor. About 10,000 lines of code were needed to build the framework, the FRP evaluator, the document model and the editor, including the implementation of the special language created for KSWorld.