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  • The Search for a Single Cause
    not mean one has found all of them There are at least two documented coding errors in the Therac 25 case but no real assurance that these are the only ones Email made it easy for Machado to verbally attack others but other technologies would have worked well too Hughes Microelectronics was cited for particular flaws in its inspection system but the larger culture of safety was in need of

    Original URL path: http://computingcases.org/general_tools/teaching_with_cases/general_pitfalls/pitfalls_single_cause.html (2016-04-30)
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  • Subjectivity in Thinking About Causes
    individual in the role play If you have read all of the Therac 25 case we present you have a god s eye view of the action like the reader of a classic novel But the people inside the case never had the convenience of this view and might not even be able to agree now on a single hindsight driven account after the fact Once you can firmly grasp the limited nature of each individual s knowledge about what was going on at any particular time you can then progress to further ambiguity about how people might be personally or professionally motivated to find one kind of cause for an accident more likely than another It may be that the AECL technicians were simply handicapped by their limited knowledge when they thought an electric shock might be the cause of the first accident in Tyler TX But it was also a convenient cause in that it was not AECL s problem A note of caution here It is easy to become cynical and to invent conspiracies and evil motivation for everyone Resist this temptation Cynicism is the easy way to appear sophisticated about a case but it is often

    Original URL path: http://computingcases.org/general_tools/teaching_with_cases/general_pitfalls/pitfalls_subjectivity.html (2016-04-30)
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  • The Search to Affix Blame
    Preferably there is only one culprit but if there are several they should be in a conspiracy together But consider for a moment it is completely feasible that LaRue and Saia in the Hughes case are acting independently are both guilty of at least skirting the truth but have not explicitly conspired together If you are not convinced of this read the Saia gets a call scenario to see how Saia might put pressure on LaRue to skip required tests but not explicitly encourage it This search for a psychologically satisfying explanation may be fine for coffeehouse conversation but engineers responsible for the operation of the system should look beyond it for two reasons First if safety is a system property as Safety Engineering and the ImpactCS model imply then focussing on only one level of the system will mislead us about the complexity of the issues Simply blaming Machado for the email harassment does not lead us to look for the more complex ways that the culture of information sharing made this harassment easier Nor does it help us make a more secure system Second a focus on individual or corporate blame implies only one kind of solution people

    Original URL path: http://computingcases.org/general_tools/teaching_with_cases/general_pitfalls/pitfalls_blame.html (2016-04-30)
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  • The Rush to Legalism
    in our study so individuals can determine how to avoid being sued We include it so we can understand how a system works to either provide safety or to make accidents more likely It is quite easy to make distinctions between what is legal and what is moral Neither set is contained entirely by the other though they do overlap One can think of actions that are legal but not

    Original URL path: http://computingcases.org/general_tools/teaching_with_cases/general_pitfalls/pitfalls_legalism.html (2016-04-30)
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  • The Loose Ascription of "Human Error"
    will find itself having to cope with human error But explaining the Therac 25 accidents as due to human error suggests there is nothing that could have been done to prevent it other than telling people to be more careful see affixing blame above The fields of Computer Human Interaction and of Human Factors are based on the idea of accommodating the propensities of humans by adapting both to their

    Original URL path: http://computingcases.org/general_tools/teaching_with_cases/general_pitfalls/pitfalls_ascription.html (2016-04-30)
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  • A Fixation on the Technical Failures (and Fixes) in the System
    too narrow focus on these can lead one to think that simply fixing each one as it occurs is the appropriate action For instance one might think that the child safety problem with early refrigerators was that the latch could not be opened from the inside if a child was trapped inside A narrow focus on this might lead one to add a child detector to the refrigerator that opens the latch when this troublesome condition occurs This now leaves us with an additionally complicated system with more points of failure Rethinking the design of the product allows one to see that one does not need latches to close refrigerator doors magnets will do fine In a similar manner we have several examples in the Therac 25 case of fixation on technical failures The initial response of AECL involved pinpointing a microswitch failure as the problem The claim that the technical fix to this produced a five order of magnitude increase in safety suggests that AECL felt this fix was the single solution It took more than a year of negotiation with the FDA to get a plan from AECL that involved more systemic redesign issues One might ask the

    Original URL path: http://computingcases.org/general_tools/teaching_with_cases/general_pitfalls/pitfalls_tech_failures.html (2016-04-30)
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  • Concluding Comments
    Concluding Comments We mention these pitfalls to give you some idea of what not to do Conceptually most of them share a preference for unwarranted simplicity of explanation in complex systems Students will have some trouble dealing with these cases

    Original URL path: http://computingcases.org/general_tools/teaching_with_cases/general_pitfalls/pitfalls_conclusion.html (2016-04-30)
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  • Why the tests
    talk of basic rights Research supports this observation see Keefer M Ashley K D 2001 Case based Approaches to Professional Ethics A Systematic Comparison of Students and Ethicists Moral Reasoning Journal of Moral Education 30 377 398 Both of these kinds of reasoning are usually at a low level and unanalyzed Students often do not even know they are switching between them or how the appeals differ The ethics tests make the contrasts among the different types of tests explicit and apparent Students learn that they are different and that occasionally they disagree Just learning this much is a useful achievement In addition the tests help the student learn that ethical decision making is not simply a matter of applying rules The rules in the guise of these ethics tests often don t establish a definitive answer or even a set of definitive answers The most help they can provide is to guide thinking on the issues and to rule out some clearly inappropriate choices The tests also provide some structure when evaluating a set of options We have argued in the section on teaching with cases that some structure is necessary and this structure is a reasonable one with

    Original URL path: http://computingcases.org/general_tools/teaching_with_cases/ethics_tests/why_the_tests.html (2016-04-30)
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