TECHNICAL CONSIDERATIONS FOR COMPUTER BASED SYSTEMS

Section 2 provides recormnendations on the technical considerations for computer based systems, addressing advantages and disadvantages of such systems, safety and reliabihty issues, and some organizational preconditions of the system development project. 

Section 3 provides recormnendations on the application of requirements for management of safety to computer based systems important to safety. 

Section 4 provides recormnendations on the plarming phase of the system development project, and describes the structure and content of the associated documentation, including the development plan, the quahty assurance programme description, the verification and validation plan, and the configuration management plan. 

In relation to the assessment of safety and reliability, computer based systems have two basic properties. They are programmable and their hardware is based on 

These advantages are counterbalanced by a number of disadvantages. Software implementation tends to be more complex and therefore more prone to design errors than implementation of purely hard-wired systems. Moreover, software implementations are discrete logic models of the real world. This has two types of consequences. Software is more sensitive (i.e. less tolerant) to small errors. It is also more difficult to test, because interpolation and extrapolation are much more difficult to apply to computer based systems than to traditional analog systems, and ultimately are not entirely valid. 

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