Assessment of failures due to human interventions in “Formal Specification & Verification” of a Safety Critical system 1 Abstract—In Safety Critical Systems, failure means a hazardous situation or even loss of life. Errors are unacceptable in SCS. Formal methods are used to minimize the impact of ambiguous requirements. FM’s varies with domains. Development process involves domain experts, safety engineers and software engineers. They do formal specification & verification of the requirement which varies according to the safety standards. This process is depending upon the human interventions with the tools or at the time of specifying the properties of the system. That’s why we are not at the stage to claim a fully fault free reliable system. Index Terms—Safety Critical System, Formal Specification, Formal verification, Safety Standards, System analysis I. INTRODUCTION HIS term paper presents a literature review on formal specification and verification of Safety Critical systems in different areas such as railways, avionic, medical, embedded systems, space and nuclear systems. Literature review covers the basics artifacts of developing a safety critical system i.e. Guidelines, Safety requirements, analysis, use of safety standard, anal minimizing the gap between software engineer and safety engineer. In Safety critical systems, failure means a disaster and can lead to loss of life[1]. The most important factor of safety critical system is to remain it fault free. This is possible through formal methods. Formal methods use mathematical models based on logic and set theory to remove the ambiguity, inconsistency, redundancy and incompleteness from the requirement. It is to be studied that systems develops through formal methods are more stable than the system developed through textual requirements[2]. Formal Specification are the form of requirements in mathematical shape which is done by formal methods. Formal specification act as medium in the communication process between requirement analyst and developers of the system. Formal Specification demonstrates the systems behavior in abstract form of notations. Formal Specification reduce the errors at early stages of life. Formal specification affirms the requirements did not infer two meanings at runtime. Output of the formal specification directly used as input of formal verification techniques[3]. Formal Verification techniques affirms that formal specifications meets the requirements of the systems or not. It ensures and checks the correctness of the behavior of the system[4]. Formal verification is also one of the formal method technique, which verifies the properties of systems written in temporal logic and gives output in binary[5]. Formally verified requirements are the inputs for software developer. Model checking [6] and Theorem Proving[7] is the most popular techniques for formal verification Different domain areas of safety critical systems have established bodies i.e. RTCA, HSE, AECB ESA, RIA [8]. These bodies defined set of rules and guidelines for the development of safety critical systems. Different domains endorsed different formal methods for formal specification and formal Muhammad Farooq Research Student at “National University of Computer Emerging Sciences, NUCES, Islamabad” (email: i191235@nu.edu.pk) Assessment of failures due to human interventions in “Formal Specification & Verification” of a Safety Critical system T