Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. XML User Interface (XUI) is a Java and XML framework for building rich client, desktop and mobile applications. The framework can save much of the code typically needed to build an application with consequent savings in development time, maintenance costs and hence results in greater stability. The framework supports data binding, event handling, validation and includes a NetBeans plug-in for interactive creation of the user interface. The project also features some innovative features such as an implementation of the new synth Look and Feel using SVG plus an interactive layout manager using guidelines. The XUI framework is released under the Mozilla Public License and can be downloaded free of charge.