Computers And Safety

Question 1

Failure

Answer 1

Observed to not do what it is supposed to visible indicating a problem
Ex) segmentation fault

Question 2

Fault

Answer 2

Cause of visible behaviour, could be from more then one error
Ex) variable assigned to null

Question 3

Error

Answer 3

The human mistake that caused the fault to occur

Ex) did not check for nulls

Question 4

What can go wrong

Answer 4

Error free software very difficult
Failures from more then one error or factor
Want to try to reduce errors by following good software procedures and practices
Small and simple gives confidence

Question 5

Problems for individuals

Answer 5

Most often in their role as consumers
Incorrectly targeted in database
Billing errors

Cause- large diverse population, overconfidence in accuracy, not updated, lack of accountability

Question 6

System failures

Answer 6

Affecting number of people and can be large amount of money
Communications - telephone 
Business- inventory software 
Financial- stock exchange 
Transportation- reservations, tickets

Causes- insufficient testing, significant changes, overconfident in system, mismanagement of project

Question 7

Safety critical applications

Answer 7

Property may be damaged or destroyed or people injured or killed
Domains- medicine, aircraft, trains

Cause- lack of override features, insufficient testing, sheer complexity, overconfidence, mismanagement

Question 8

Development process

Answer 8

Size- amount of people involved 
Dynamism - vision or requirements change per month
Critically- if fails what outcome 
Culture- tolerate changes or not
Personal- experience 

Closer to centre more agile
Further out more plan based - talk to all stakeholders and map everything

Question 9

What goes wrong

Answer 9

Job they are doing is difficult or done poorly

Can have overconfidence and reused systems that won’t work in different environments

Intellectual overload