1. Introduction
The development of avionics software products has to conform to the DO-178C [17] standard. DO-178C provides a set of certification objectives aimed at guiding the development of avionics software products. The results of all development processes must be then verified for compliance with the certification objectives. Verifying software products can be a complex task. The verification, according to DO-178C, is performed by reviews, analysis, or tests. However, when using formal methods, DO-178C recommends to make use of the guidelines provided by RTCA DO-333 [16], which is a supplement to DO-178C. DO-333 identifies the modifications and additions to DO-178C objectives, activities, and software life cycle data that should be addressed when formal methods are used as part of the software development process. It includes artifacts that would be expressed using some formal notation and the verification evidence that could be derived from them.