In the Therac case we describe the safety issue associated with the implementation of a computing system in a real sociotechnical system. In this case, the safety concerns occur at the manufacturing level rather that the implementation level. This bring home the point that a sociotechnical system needs to include those systems that contribute to its manufacture. And it highlights the ethical responsibilities of computing professionals to design systems that take into account the way components are designed in the real world.

Of course, it is impossible to design a system to avoid fraud on the part of component suppliers. But one can certainly think about the needed redundancy to make a system work even if some of its parts fail. The estimates of this needed redundancy need to take into account the likelihood that all the parts that are delivered may not be up to specification. This can dramatically increase the likelihood of component failure and make redundancy more important.

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