CSSE3002 Lecture Notes - Lecture 10: Motor Industry Software Reliability Association, Cyclomatic Complexity, Functional Safety
28 Jun 2018
School
Department
Course
Professor
Killer Code (Guest Lecture)
Picture: Sword of Damocles – Damocles fond over the king and the king suggested him that
they should swap places for a day, Damocles took the offer, king let him sit on the throne
that has a sword suspended above his head with a horse hair. Hence Damocles were eager
to get off the seat. – power and responsibilities has an amount of danger to it. – perhaps that
element of danger outweighs the benefits of being on the position.
Functional Safety – a programmable system that needs to perform a function – needs to be
safe
e.g. train, plane, operating theatre, space programs etc
How to ensure a product doesn’t do something else that it isn’t supposed to do? – this talk
will give examples about case studies
Therac-25
-Medical device – radiotherapy – two modes (fires electron beams in low energies,
electron beams with high energy x-ray but needs the plate to make the ray safe for
the patient)
-Without the plate, could be harmful
-Previous model of Therac had hardware interlock that ensures that the beam couldn’t
be produced unless if the plate is there to protect the patient (mid 80s)
-Nowadays there is software – wants to save cost – new model – software had some
issues, wasn’t exposed in testing – overdosed the patient – at least 3 people died
from that bug
Health software
-E.g. Get medication wrong
-Programmers did not think of the consequences that will bring along with the faults in
the software (treat the software as something that helps the hospitals only)
From systems perspective, the risk managed should be controlled and have a process. It is
a part of the job of a system engineer to perform the hazard analysis. As a software
engineer, tend to work in a slightly lower level, usually given a set of safety requirements.
Risk Matrix
-Measuring the likelihood of a risk occurring and its severity
-Estimate the likelihood and the impact, plot it on the matrix and move it
-Try to reduce the impact, likelihood, or both
-Likelihood:
orates, underlying failure rate, what proportion of those failures are dangerous,
what proportion we can detect and safely react to
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Hence damocles were eager to get off the seat. Power and responsibilities has an amount of danger to it. Perhaps that element of danger outweighs the benefits of being on the position. Functional safety a programmable system that needs to perform a function needs to be safe e. g. train, plane, operating theatre, space programs etc. This talk will give examples about case studies. Medical device radiotherapy two modes (fires electron beams in low energies, electron beams with high energy x-ray but needs the plate to make the ray safe for the patient) Previous model of therac had hardware interlock that ensures that the beam couldn"t be produced unless if the plate is there to protect the patient (mid 80s) Nowadays there is software wants to save cost new model software had some issues, wasn"t exposed in testing overdosed the patient at least 3 people died from that bug.
