Appropriateness of user interfaces to tasks

In this paper we define the complex relation between task models and user interfaces in a declarative manner. We do this by describing how a task model can be transformed to other functionally equivalent task models, how it can be mapped to a user interface prototype, and how a user interface can be transformed to other functionally equivalent user interfaces. We use this relation in order to tackle the question whether a user interface is appropriate for a task, which leads us to a conceptual notion of usability. The user interfaces are modeled with form-oriented analysis.