A Formal Approach to Connectibility Affordances

Connectibility affordances, or opportunities for a user to establish input/output cable connections, can be critical to the safety and usability of complex systems. To support model-based analyses, this research introduces a formal approach: Connectibility Affordance VErification, Modeling, and ENumeration (CAVEMEN). CAVEMEN is applicable to a human-environment system encompassing physical entities with specified properties, a user with specified motor abilities, and connectibility affordance instances involving different combinations of source-target connections. The modeling technique leverages object-oriented principles to define one instance of a connectibility affordance with respect to one unique combination of connection sources and targets. An inspection technique supports the enumeration of connectibility affordance instances that are desired (supporting a correct connection) and undesired (supporting an incorrect connection). A model checking technique aids in verifying accuracy, meaning the user can actualize desired affordance instances, and robustness, meaning undesired affordance instances never emerge. An XML-based grammar, a model checking syntax translation tool, and a linear temporal logic specification of accuracy and robustness support the analyses. We demonstrate CAVEMEN with a pacemaker system case study. The inspection aids in identifying nine desired and 18 undesired instances of chamber-port connectibility. The trace evaluation shows that accuracy and robustness depends on whether an entity property of interest can change in the environmental context. These results indicate that CAVEMEN shows promise for analyzing connectibility affordances of a safety-critical system.