system errors and failures Flashcards
what are the different types of errors
regulatory; lack of regulation/ not trained enough
hardware; failure in design/ not the right requirements
software; specification/ requirements testing
managerial; safety climate/ quality control
human; skips/ mistakes
why is it bad to have failures in complex systems
failure in one section can cause a failure in another
there are many combinations on how things can go wrong
complex interactions
unfamiliar, unplanned, unexpected sequences which are not noticeable or immediately comprehensible and are usually interdependent
tightly coupled
time dependant processes which are rigidly ordered with very little slack
explain how the Swiss cheese model works
the holes represent unintended weaknesses and when they line up they get through all barriers leading to failures
latent errors
only evident when combined with other errors and creates a breach but usually they’re not an issue
limitations of the Swiss cheese model
layers of defence can interact with support and erode each other
doesn’t explain anything about the holes
dependability
how confident the user is that the system will operate
trust in the system that’s justified
what are the 3 main arts of lapries model of dependability
implements; faults, errors, failures
means; fault avoidance/prevention
primary attributes; availability, reliability, safety, security
human error
the failure to perform a task correctly
types of human actions
skills based performance; becomes routine
rules based performance; following rules and procedures
knowledge based performance
types of human error
slips; execution failure- intentions are correct but not carried out well
lapses; execution failure - forgetting to do something
mistakes; planning failures - wrong actions carried out
