Question 1

Some computer errors are actually system failures, in that it was the human/computer interface which caused the resulting problem.

Accepted Answer

A) True 
 B)False  True

Question 2

Some people have proposed establishing legal standards and regulations to govern safety-critical computer-based systems. 
a. Give and explain a few of the best arguments for and against such a proposal (at least two on each side). Give counter-arguments against the arguments for each side.
Note: the "counter-arguments"
you are asked to give should oppose or answer the arguments on the other side as directly and convincingly as possible. They should not be simply unrelated arguments on the opposite side of the issue.
b. Describe two provisions that may be included in such regulations. How effective do you feel each provision would be?

Accepted Answer

Some of the best arguments for establishing legal standards and regulations to govern safety-critical computer-based systems include the need for accountability and responsibility. By implementing regulations, there is a clear framework for holding individuals and organizations accountable for any safety failures that may occur. This can help prevent negligence and ensure that proper precautions are taken to protect the public. Additionally, regulations can provide a level playing field for all companies, ensuring that they are all held to the same safety standards.

Counter-argument: However, some may argue that regulations can stifle innovation and hinder technological advancements. They may claim that strict regulations could slow down the development and implementation of new technologies, ultimately doing more harm than good.

Another argument for regulations is the protection of public safety. By implementing standards, there is a greater assurance that safety-critical systems will be reliable and secure, reducing the risk of potential harm to individuals and society as a whole.

Counter-argument: On the other hand, opponents may argue that regulations can create a false sense of security. They may claim that simply having regulations in place does not guarantee that safety-critical systems will be foolproof, and that individuals may become complacent in their reliance on these regulations.

Two provisions that may be included in such regulations are regular safety audits and mandatory reporting of safety incidents. Regular safety audits would require companies to regularly assess and evaluate the safety of their systems, ensuring that they are up to standard and identifying any potential risks. Mandatory reporting of safety incidents would require companies to report any safety failures or incidents, allowing for transparency and accountability.

The effectiveness of each provision would depend on the enforcement and oversight of these regulations. Without proper enforcement, these provisions may not be effective in ensuring the safety of computer-based systems. However, if rigorously enforced, these provisions could significantly improve the safety and reliability of safety-critical systems.

Question 3

a. Briefly describe the major factors that contributed to the failure of each of the following: the Denver Airport baggage system failure, the Ariane 5 rocket malfunction, and an A320 Airbus crash. 
b. Briefly describe how professional techniques for increasing reliability and safety could have prevented these failures.

Accepted Answer

a. The Denver Airport baggage system failure was primarily due to technical issues with the automated system, including software glitches and mechanical failures. The Ariane 5 rocket malfunction was caused by a software error in the rocket's guidance system, leading to a catastrophic failure shortly after launch. The A320 Airbus crash was the result of a combination of pilot error, mechanical failure, and inadequate training.

b. Professional techniques for increasing reliability and safety could have prevented these failures by implementing thorough testing and quality control measures for the Denver Airport baggage system, conducting rigorous software testing and verification for the Ariane 5 rocket, and providing comprehensive pilot training and implementing advanced safety features for the A320 Airbus. Additionally, regular maintenance and inspection protocols, as well as a culture of open communication and reporting of potential issues, could have helped to identify and address potential problems before they led to catastrophic failures. Overall, a proactive approach to risk management, thorough testing and verification, and a commitment to continuous improvement in safety and reliability would have been key in preventing these failures.

Question 4

Most of the delay in the opening of the Denver International Airport was because of problems with

Accepted Answer

A)  the air traffic control system 
B)  the environmental monitoring systems 
C)  the baggage handling system 
D)  the telephone and communications systems

Question 5

Briefly explain the Therac-25 case. What happened? What are some reasons the machine failed? Why were there so many incidents?

Accepted Answer

The answer of Briefly explain the Therac-25 case. What happened?...

Question 6

MATCHING
-TCAS

Accepted Answer

A)  a computerized machine that gave lethal radiation overdoses to some cancer patients 
B)  operate in difficult environments where failures can have extreme consequences 
C)  detects a potential in-air collision of two planes and directs the pilots to avoid each other

Question 7

The cause of failure in a computer program is often due to more than one factor.

Accepted Answer

A) True 
 B)False

Question 8

List two principles for producing software that might have prevented the crash of American Airlines Flight 965 near Cali, Columbia in 1995. Briefly describe what each one is and how it might have made a difference.

Accepted Answer

The answer of List two principles for producing software that...

Question 9

One of the sources of failure common to BOTH the Therac-25 and the Ariane 5 rocket was

Accepted Answer

A)  confusing and poorly-documented error messages 
B)  poor human-computer interface design 
C)  operator error 
D)  reuse of software from previous versions of the systems

Question 10

Legacy systems are typically reliable, but inflexible.

Accepted Answer

A) True 
 B)False

Question 11

MATCHING
-Therac-25

Accepted Answer

A)  a computerized machine that gave lethal radiation overdoses to some cancer patients 
B)  operate in difficult environments where failures can have extreme consequences 
C)  detects a potential in-air collision of two planes and directs the pilots to avoid each other

Question 12

Which of the following occupations can sometimes cause Repetitive Strain Injuries (RSI)?

Accepted Answer

A)  Sign-language interpreter for the deaf 
B)  Musician 
C)  Computer programmer 
D)  All of the above

Question 13

A feature of high reliability organizations is loose structure.

Accepted Answer

A) True 
 B)False

Question 14

a. Describe the role the manufacturer, the hospitals/clinics, and the programmer each played in the Therac-25 radiation overdose incidents.
b. Briefly describe how professional techniques for increasing reliability and safety could have prevented the problems.

Accepted Answer

The answer of a. Describe the role the manufacturer, the...

Question 15

U.S. and European pilots are now trained to follow Traffic Collision Avoidance System (TCAS) instructions even if they conflict with instructions from an air traffic controller.

Accepted Answer

A) True 
 B)False

Question 16

MATCHING
-HROs

Accepted Answer

A)  a computerized machine that gave lethal radiation overdoses to some cancer patients 
B)  operate in difficult environments where failures can have extreme consequences 
C)  detects a potential in-air collision of two planes and directs the pilots to avoid each other

Question 17

Redundancy and self-checking are often present in safety-critical systems.

Accepted Answer

A) True 
 B)False

Exam 8: Errors, Failures, and Risks

Some computer errors are actually system failures, in that it was the human/computer interface which caused the resulting problem.

Most of the delay in the opening of the Denver International Airport was because of problems with

Briefly explain the Therac-25 case. What happened? What are some reasons the machine failed? Why were there so many incidents?

MATCHING -TCAS

The cause of failure in a computer program is often due to more than one factor.

List two principles for producing software that might have prevented the crash of American Airlines Flight 965 near Cali, Columbia in 1995. Briefly describe what each one is and how it might have made a difference.

One of the sources of failure common to BOTH the Therac-25 and the Ariane 5 rocket was

Legacy systems are typically reliable, but inflexible.

MATCHING -Therac-25

Which of the following occupations can sometimes cause Repetitive Strain Injuries (RSI) ?

A feature of high reliability organizations is loose structure.

a. Describe the role the manufacturer, the hospitals/clinics, and the programmer each played in the Therac-25 radiation overdose incidents. b. Briefly describe how professional techniques for increasing reliability and safety could have prevented the problems.

U.S. and European pilots are now trained to follow Traffic Collision Avoidance System (TCAS) instructions even if they conflict with instructions from an air traffic controller.

MATCHING -HROs

Redundancy and self-checking are often present in safety-critical systems.