Challenges such as concept, tools, and methods used in the fields, safety and security, arise during research on either field. The big gap between the two fields is resulted from the fact that research focused on either one of these two fields given that each of which has its own development tools and methods. For security requirements analysis and elaboration by the use goals KAOS notion, the goal notion allows the expression of security requirements patterns in terms of anti-goals notion and vulnerabilities of the system that is being studied. These patterns can also include a definition of the solution, or counter measure, to the attack in terms of goals that avoid a given vulnerability. For safety-critical systems, it is very important to deal with obstacles KAOS notion, which capture undesired properties. It allows analysts to identify and address exceptional circumstances during requirements engineering in order to produce robust or new requirements to avoid or reduce the impact of obstacles giving more reliable software.