Towards a Formal Approach to Validating and Verifying Functional Design for Complex Safety Critical Systems

The quality and reliability of safety criticalsoftware systems are highly dependent on proper systemvalidation and verification. In model-driven softwaredevelopment, semi-formal notations are often used inrequirements capture. Though semi-formal notations possessadvantages, their major disadvantage is their imprecision. Atechnique to eliminate imprecision is to transform semi-formalmodels into an analyzable representation using formalspecification techniques (FSTs). With this approach to systemvalidation and verification, safety critical systems can bedeveloped more reliably. This work documents early experienceof applying FSTs on UML class diagrams as attributeconstraints, and pre- post-conditions on procedures. Thevalidation and verification of the requirements of a system tomonitor unmanned aerial vehicles in unrestricted airspace is theorigin of this work. The challenge is the development of a systemwith incomplete specifications; multiple conflicting stakeholders’interests; existence of a prototype system; the need forstandardized compliance, where validation and verification areparamount, which necessitates forward and reverse engineeringactivities