At present, the spread of hand held devices with growing computing power and functionality allows that different interaction elements can be distributed among a wide range of devices from different platforms, supporting interaction with one or many users. To take advantage of the benefits this kind of devices provides, traditional user interfaces have been evolving towards distributed user ones. The specification of the constraints on the way in which these elements can be distributed is still an open field and further research is needed. In this paper we propose a new schema-based definition of Distributed User Interfaces (DUIs), allowing the specification of the elements to be distributed, defining constraints on the distribution process itself, independently of the language selected to construct the interface. Thus, the interface distribution process becomes the creation of an XML instance from a grammar specified in Schema language. We also introduce two new definitions to complete the formalization of our previous definition of DUI. Our previously defined Abstract User Interface (AUI) model jointly with this new schema-based definition of DUIs will lead us to the full specification of concrete DUIs. We provide some examples of the distribution process using the proposed schema.

distributed user interfaces, formal models, schemas