Using Object-Z to specify a web browser interface

A specification describes the functions which a system provides to its users without explanation of how those functions are implemented. A specification of an interactive system's user-interface is an abstract description of the interactive system itself. Such a specification indicates which functional aspects of the system are perceivable by the user and the logical organisation of information provided by the interface. To illustrate, we specify the user-interface for a World-Wide-Web browser. We use Object-Z, a formal specification and design language. Formal methods are increasingly accepted for specifying functional aspects of software systems, however their use in user-interface development is less common. This is despite widespread support for the view that formal methods ease system development. We demonstrate that Object-Z can be used to specify, the user-interface for an interactive system. Such a specification may form the basis for an Object-Z user-interface design.