Trust, Safety & ReliabilityINTRODUCTION TO COMPUTER ERRORS

TEXTBOOK: BRINKMAN’S ETHICS IN A COMPUTING CULTURE

READING: CHAPTER 5, PAGES 150-155, 160-163.

Computer errors•A range of possible consequences– Seconds lost, other inconvenience– Data lost– $ - $$$– Injuries and deaths

•Examples:– Disfranchised voters– False arrests– Price & billing errors– Air traffic control, airplane control

The Apocalypses That Might Have Been

Apocolypse cont’d

Hardware Errors•Failure of the physical components of the computer system

Software Errorso “Bugs”

o Bug v. mistake debate

◦ Ariane 5◦ ariane 5 explosion – YouTube◦ Floating point number storage

◦ Arithmetic overflow

Computer Solves the Wrong Problem • Complexity of programming: garbage in, garbage out

• Gemini 5, 105 miles off landing target: • Earth’s rotation is not 360° in 24 hr but 360.98°

• Friendship 7, 40 miles off landing target:• Failure to take into account weight loss in aircraft due to use of

consumables

Misuse The Hernandez situation:

◦ Roberto Hernandez was pulled over running a stop sign◦ When the officer ran his license the officer was convinced that he was dealing with a wanted man,

Roberto Hernandez

Same birthday, similar height, weight, tattoo.

Officer was convinced that the name difference was a mistake in the system. It was not.

Communication Failure Misunderstandings

◦ Of what the system is capable of or how it works

◦ See example of airliner running out of fuel◦ http://en.wikipedia.org/wiki/Gimli_Glider

Special Topic: Electronic Voting Electronic voting machines:

◦ After the "hanging chad" controversy of the 2000 election, Congress passed a federal law that gave states funding to replace their punch card and lever voting systems with electronic voting machines

Implementation of electronic voting

North Carolina 2004◦ Voting machine manufacturer said the electronic voting machine could handle 10,500 votes each

◦ Reality – could only hold 3,005 votes◦ Result – lost 4,530 votes

Many voting machines do not create a paper trail◦ Voting machines used by as many as a quarter of American voters in 2012 can be hacked with just $26

in parts and an 8th grade science education◦ Vulnerability Assessment Team at Argonne National Laboratory ◦ The experts say the hack could change voting results while leaving absolutely no trace of the

manipulation behind

System testing

◦ Flaws in modeling real events◦ Verification: does the computer program correctly implement program?

◦ Not understanding all relevant issues◦ Validation: does the model accurately represent the real system?