Texas State CS 2315 - Computer Reliability

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Copyright © 2009 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Chapter 7:! Computer Reliability Ethics for the Information Age Third Edition by Michael J. Quinn1-2 Copyright © 2009 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 7-2 Chapter Overview • Introduction • Data-entry or data-retrieval errors • Software and billing errors • Notable software system failures • Therac-25 • Computer simulations • Software engineering • Software warranties1-3 Copyright © 2009 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 7-3 Introduction • Computer systems are sometimes unreliable – Erroneous information in databases – Misinterpretation of database information – Malfunction of embedded systems • Effects of computer errors – Inconvenience – Bad business decisions – Fatalities1-4 Copyright © 2009 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 7-4 Data-Entry or Data-Retrieval Errors • A computerized system may fail because wrong data entered into it • A computerized system may fail because people incorrectly interpret data they retrieve1-5 Copyright © 2009 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 7-5 Disfranchised Voters • November 2000 general election • Florida disqualified thousands of voters • Reason: People identified as felons • Cause: Incorrect records in voter database • Consequence: May have affected election’s outcome1-6 Copyright © 2009 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 7-6 False Arrests • Sheila Jackson Stossier mistaken for Shirley Jackson – Arrested and spent five days in detention • Roberto Hernandez mistaken for another Roberto Hernandez – Arrested twice and spent 12 days in jail • Terry Dean Rogan arrested after someone stole his identity – Arrested five times, three times at gun point1-7 Copyright © 2009 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 7-7 Accuracy of NCIC Records • March 2003: Justice Dept. announces FBI not responsible for accuracy of NCIC information • Exempts NCIC from some provisions of Privacy Act of 1974 • Should government take responsibility for data correctness?1-8 Copyright © 2009 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 7-8 Dept. of Justice Position • Impractical for FBI to be responsible for data’s accuracy • Much information provided by other law enforcement and intelligence agencies • Agents should be able to use discretion • If provisions of Privacy Act strictly followed, much less information would be in NCIC • Result: fewer arrests1-9 Copyright © 2009 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 7-9 Position of Privacy Advocates • Number of records is increasing • More erroneous records → more false arrests • Accuracy of NCIC records more important than ever1-10 Copyright © 2009 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 7-10 Analysis: Database of Stolen Vehicles • > 1 million cars stolen every year – Owners suffer emotional, financial harm – Raises insurance rates for all • Transporting stolen car across a state line – Before NCIC, greatly reduced chance of recovery – After NCIC, nationwide stolen car retrieval • At least 50,000 recoveries annually due to NCIC • Few stories of faulty information causing false arrests • Benefit > harm → Creating database the right action1-11 Copyright © 2009 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 7-11 Software and Billing Errors • Assume data correctly fed into computerized system • System may still fail if there is an error in its programming1-12 Copyright © 2009 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 7-12 Errors Leading to System Malfunctions • Qwest sends incorrect bills to cell phone customers • Faulty USDA beef price reports • U.S. Postal Service returns mail addressed to Patent and Trademark Office • Spelling and grammar error checkers increased errors • BMW on-board computer failure • Temporarily out-of-control Boeing 7771-13 Copyright © 2009 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 7-13 Errors Leading to System Failures • Los Angeles County + USC Medical Center laboratory computer • Japan’s air traffic control system • Chicago Board of Trade • London International Financial Futures and Options Exchange • Comair’s Christmas Day shutdown1-14 Copyright © 2009 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 7-14 Analysis: E-Retailer Posts Wrong Price, Refuses to Deliver • Amazon.com in Britain offered iPaq for £7 instead of £275 • Orders flooded in • Amazon.com shut down site, refused to deliver unless customers paid true price • Was Amazon.com wrong to refuse to fill the orders?1-15 Copyright © 2009 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 7-15 Rule Utilitarian Analysis • Imagine rule: A company must always honor the advertised price • Consequences – More time spent proofreading advertisements – Companies would take out insurance policies – Higher costs → higher prices – All consumers would pay higher prices – Few customers would benefit from errors • Conclusion – Rule has more harms than benefits – Amazon.com did the right thing1-16 Copyright © 2009 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 7-16 Kantian Analysis • Buyers knew 97.5% markdown was an error • They attempted to take advantage of Amazon.com’s stockholders • They were not acting in “good faith” • Buyers did something wrong1-17 Copyright © 2009 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 7-17 Notable Software System Failures • Patriot Missile • Ariane 5 • AT&T long-distance network • Robot missions to Mars • Denver International Airport • Direct recording electronic voting machines1-18 Copyright © 2009 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 7-18 Patriot Missile • Designed as anti-aircraft missile • Used in 1991 Gulf War to intercept Scud missiles • One battery failed to shoot at Scud that killed 28 soldiers • Designed to operate only a few


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Texas State CS 2315 - Computer Reliability

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