(Re)presentation in XForms

XForms [6][7] is an XML-based declarative programming language. XForms programs have two parts: the form or model, contains descriptions of the data used, and constraints and relationships between the values that are automatically checked and kept up to date by the system; and the content, which displays data to the user, and allows interaction with values. Content is presented to the user with abstract controls, which bind to values in the model, reflecting properties of the values, and in general allowing interaction with the values in various ways. Controls are unusual in being declarative, describing what they do, but not how they should be represented, nor precisely how they should achieve what is required of them. The abstract controls are concretised by the implementation when the XForm application is presented to the user, taking into account modality, features of the client device, and instructions from style sheets. This has a number of advantages: flexibility, since the same control can have different representations depending on need and modality, device independence, and accessibility. This paper discusses how XForms content presentation works, and the requirements for controls, discusses how one implementation, XSLTForms, implements content presentation, and the use of CSS styling to meet the requirements of controls, and future improvements in both.