Back in Systems 001 I was taught that an overloaded system, be it a reactor control or SDI, failed due to overload in the following manners: 1. Sacrificed quality of work. 2. Sacrificed throughput rate. 3. Failed catastrophically (crashed). 4. Any combination of the above. Can a given system be designed to fail in a _chosen_ manner, so that it does not crash - i.e. "graceful degradation." Of course. I see no reason why new systems cannot do the same - at least in regard to the overload portion of the problem. - firstname.lastname@example.org
Undoubtedly we can load sensors on a system until it will no longer fly, move, fight, or whatever due to the number of sensors. Airplane cockpits already provide more information than pilots can handle. Combat sensor systems provide more data than battle-managers can handle. On the early space flights we even instrumented the astronauts themselves -- in a manner that should not be discussed on a family forum. There seems little point in providing a cockpit display of the pilot's rectal temperature; but on the ground someone cared. One of the functions being performed by computers today is to filter the information, so that the system operator sees relevant data. One of the tough parts is to decide what is relevant. I submit that "operator assistant" computers deserve special care in design and testing. They seem to be used where lives are at stake, and where data is available. Relying on the computer to decide what is "relevant" in a given situation is fraught with risk. Relying on a human to decide in advance of the situation is not much better. Another area of concern is the "transition" problem discussed in previous issues. I don't know that Navy Propulsion reactors are under-computerized deliberately, accidentally or at all. Having been a watch officer in the Navy and having lived through a number of unexpected emergencies I can personally attest to the seriousness of the "transition" problem - even without computers. To be awakened from sleep with alarm bells ringing and bullhorns blaring "FIRE, FIRE, FIRE IN NUMBER TWO MAGAZINE!" - and then be standing dressed, over the magazine, and in charge of the situation in less than 60 seconds is quite an experience. That I am here to recognize the problem is due to excellent train- ing of the entire crew, not to any specific actions on my part. Frankly, I just "went automatic" and shook after it was over, not during. I suspect that any pilot, truck driver, policeman, etc. could tell a dozen similar tales. I'm not proposing any answers - except for extreme care. - email@example.com
From: prairie!dan at rsch.wisc.edu (Daniel M. Frank) Much of the concern over "perfection" in SDI seems to revolve around this model (aside from the legitimate observation that there is no such thing as a leakproof defense). I've said it before, but it bears repeating; no critic has ever said SDI software must be perfect. The only ones who say this are the pro-SDI people who are criticizing the critics. The [SDI] dialogue would be better served by agreeing on a model, or set of models, and debating the feasability of software systems for implementing them. Having a "set of models" means that those models share certain characteristics. There is one major characteristic that all SDI software will share: we will never be able to test SDI software -- whatever its precise nature -- under realistic conditions. Then the relevant question is "What can we infer about software that cannot be tested under realistic conditions?"
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