XForms is a W3C standard that was originally designed to allow the specification of form-handling on the web. However, after the release of version 1.0, it was quickly realised that with a small amount of generalisation the language could be used for more general processing and application definition. And so was born XForms 1.1.

XForms has now been in use for a number of years, and is widely used on websites, but also for other applications, such as the definition of machine interfaces, the operation of submarines, for ship-building, banking and insurance, food processing, medical research, and many others. The Dutch weather service KNMI is based on XForms; several Dutch government ministries use XForms. XForms is an integral part of ODF, the Open Office Format.

XForms has a number of unique properties when compared with most application languages. Firstly it has a strict separation of data and user-interface, allowing you to specify what might be called data sheets with initial values, types, constraints and dependencies, separately from the interface.

Secondly, the interface uses intent-based controls that only specify what the control is supposed to do, and not how it should achieve that. That means for instance that the same control can drive a menu, or a drop down list or radio buttons, depending on needs; this can be changed by style sheets for instance. This makes applications far more device-independent, since an application can adapt to its environment, rather than requiring the author to write different applications for different devices.

Thirdly, functionality is specified declaratively rather than procedurally. This reduces the size of application significantly, and vastly reduces production times and costs. In fact, many examples have shown that an order of magnitude savings can be achieved, even on huge projects.

This talk introduces the elements of XForms, and then develops a Google-maps-style application in about 100 lines of code.