  Critical human-machine interfaces are present in many systems including
avionics systems and medical devices. Use error is a concern in these systems
both in terms of hardware panels and input devices, and the software that
drives the interfaces. Guaranteeing safe usability, in terms of buttons, knobs
and displays is now a key element in the overall safety of the system. New
integrated development environments (IDEs) based on formal methods technologies
have been developed by the research community to support the design and
analysis of high-confidence human-machine interfaces. To date, little work has
focused on the comparison of these particular types of formal IDEs. This paper
compares and evaluates two state-of-the-art toolkits: CIRCUS, a model-based
development and analysis tool based on Petri net extensions, and PVSio-web, a
prototyping toolkit based on the PVS theorem proving system.
