A compositional model for the formal specification of user interface software

This thesis investigates abstractions for modelling user interface software, discussing their content and their formal representation. Specifically, it focuses on a class of models, called formal interactor models, that incorporate some of the structure of the user interface software. One such abstract model is put forward. This model is called the Abstraction-Display-Controller (ADC) interactor model; its definition draws from research into user interface architectures and from earlier approaches to the formal specification of user interfaces. The ADC formal interactor model is specified using a specification language called LOTOS. Several small scale examples and a sizeable specification case study demonstrate its use. A more rigorous discussion of the ADC model documents its properties as a representation scheme. The ADC interactor is compositional, meaning that as a concept and as a representation scheme it applies both to the user interface as a whole and also to its components. This property is preserved when interactors are combined to describe more complex entities or, conversely, when an interactor is decomposed into smaller scale interactors. The compositionality property is formulated in terms of some theorems which are proven. A discussion on the uses of the ADC model shows that it provides a framework for integrating existing research results in the verification of formally specified user interface software. Finally, the thesis proposes a conceptual and formal framework for relating interface models to models of users’ task knowledge capturing some intuitions underlying task based design approaches.