System Failures and Errors

Flashcards about System Failures and Errors.

What are the key objectives for Week 9?

To identify causes of system failure, understand theories behind system errors, and consider how to make systems more dependable.

What characterized the Titanic as a system?

A complex socio-technical system with safety-critical controls, cutting-edge technology, complex management structures, and a complex political and organizational context.

What are the elements to consider for the entire system perspective?

Technical Components, People/Knowledge/Processes, Organizational Context, Envrionment

What was the Post Office case study about?

A widespread miscarriage of justice where over 700 post office branch managers were wrongly convicted due to a faulty accounting software system (Horizon).

What was the core issue with the Horizon system in the Post Office case study?

The Horizon system had errors and bugs that falsely suggested cash shortfalls, leading to wrongful accusations of theft against branch managers.

What was a key failing in the legal system highlighted by the Post Office case study?

A legal presumption of the proper functioning of computers, which led to an over-reliance on the Horizon system's data.

What was the focus of the Boeing 737 MAX case study?

The deaths of all passengers, pilots and cabin crew in Boeing 737 Max crashes in October 2018 and March 2019

What was a major problem in the Boeing 737 MAX case study regarding design?

A software solution was chosen for what was essentially a hardware issue (engine size and plane design).

Name examples of different levels of failure?

Regulatory failures, Managerial Failures, Hardware Failures, Software Failures, Human Failures

What are the characteristics of a complex system prone to failure?

Complex interactions (unfamiliar, unplanned sequences) and tight coupling (time-dependent, rigidly ordered processes with little slack).

What are some limitations of the Swiss Cheese Model?

It assumes independence of barriers and randomness of 'hole' alignment, and doesn't fully explain the origin or interaction of these holes.

What is dependability in the context of complex systems?

A user's justified trust in a system, reflecting confidence that it will operate as expected and not fail under normal use.

In Laprie's model, what are the impairments?

Faults are the impairments in Laprie's Model.

In Laprie's model, what are the means to achieve dependability?

Fault avoidance, fault tolerance, fault removal, and fault forecasting.

In Laprie's model, what are the primary attributes of dependability?

Availability, reliability, safety, and security.

What are the secondary attributes of dependability according to Laprie’s model?

Timeliness, Survivability, Recoverability, and Maintainability

What are the key points regarding system errors and failures?

System failures result from many compounding factors, are more likely in complex systems, and dependabiility is crucial for complex systems.