Reliability and Safety What can go wrong?

Risks of Computing They support many aspects of our security: Fly by wire aircraft Patient monitoring and care administration Financial transactions Telephone networks Military surveillance and responses

Three Categories of Failures Problems for individuals System failures that affect large numbers of people or cost large amounts of money Problems in safety-critical applications

Problems for Individuals Billing Errors Not enough care - input error Not enough testing - reasonable range Not enough training

Database Accuracy Problems Info in database is not accurate Automatic entering of info - mistakes can be overlooked Erroneous duplication - copies of incorrect info can be in other systems Insufficient training - not knowledgeable enough about the system

Possible States of a Computer Functioning correctly Functioning incorrectly Down Intentionally off

Causes of Computer Failure Faulty design of software or hardware Sloppy implementation Careless or insufficiently trained users Poor user interfaces Hardware/Software malfunctions Specification errors Scope/Application inconsistency

Computer Users Perspective Should user should understand… limitations of the computers the need for proper training the need for responsible use the difference between good products and bad ones

Computer Professional Perspective The professional should… study computer failures study computer ethics

Educated Member of Society Perspective Education will… help us evaluate the reliability and safety of various computer applications help evaluate computer technology

Relevant Research Topics Architecture: hardware and software Systems engineering Reasoning; languages, techniques and engineering Requirements analysis Fault tolerance Repair and maintenance Holistic safety arguments Formal methods Real-time issues

Consumer Hardware and Software Usually have more serious errors in their first releases Regularly sold with known bugs Hardware also has flaws Tradeoff between cost, debugging, and marketing Dishonesty, denials of problems, lack of adequate response to complaints