Abstract
Traditional user interfaces are evolving toward "distributed" user interfaces according to the new technological advances, allowing one or more interaction elements distributed among many different platforms in order to support interaction with one or more users. In this new scenario, the Abstract User Interface (AUI) model has been reviewed and modified to include specific characteristics from the Distributed User Interface (DUI) point of view. This article proposes a new AUI that takes into account the possibility of distribution. Before presenting this new AUI model, the article introduces the definition of the DUI concept and its foundations using a formal notation. Together with the new AUI model, a double hierarchy of user interfaces and targets has been defined, so the type of distribution can be verified using the concept of finality introduced as an algorithm in this article. With this new algorithm it is possible to test whether a given DUI (multiple devices, multiple user interfaces) supports the user's goal in the system.