Formal methods in computer human interaction: comparison, benefits, open questions

In order to have a more focused discussion a specific case study has been selected and it will be used to compare the various approaches proposed. This case study is the specification of a subset of the functionality of a NetScapelike browser and a html page server. The proposals will have to answer a set of questions such as: can you verify usability properties on your specification? How difficult is it to translate your specification into an implementation? What kind of constructs do you use in order to structure your specification? Designers should consider issues such as: history of the performed interactions, browsability of the user interface (i.e. the use of links), non-preemptive behaviour, effective and continuous feedback about the current state of interactions.