Client Ubiquity, Avalon, XAML, Royale, XUL - and Java? Using an XML syntax to declare and generate a rich UI for service-oriented and data-driven applications is getting a lot of traction. While much of the talk is about the application model, as it should be, it's also true that approaches like XAML, Royale, and XUL all make assumptions about the ubiquity of the client containers which they target.