Modelling a cardiac pacemaker visually and formally

Embedded software in medical devices is becoming ubiquitous and increasing in content and complexity. This paper gives an outline of a visual model of a cardiac pacemaker system, a case study from the grand challenge in software verification. The model is expressed in the Visual Contract Language (VCL), a formal modelling language that describes predicates visually. From VCL diagrams it is possible to generate Z specifications. This is the first visual and formal model of one of the software verification challenges.