Description
1.Study two papers entitled (located in the Readings folder)
No silver bullet published in IEEE Computer
The software engineering silver bullet conundrum published in IEEE Software
Based on this material, what are, in your opinion, the two most essential factors making softwaretesting activities difficult? Distinguish between technical and non-technical (say, organizational, human, etc.) factors. Justify your opinion; provide some convincing arguments. Are these factors
associated with inherent or accidental difficulties?
Value 20 points
2. Discuss an example of a serious software failure in 2020. For this, complete some Web searchand literature review. Clearly identify a source of your information (e.g., include a link to thewebsite). Describe a nature of the software failure. Identify its origin. Were there any softwaretesting efforts mentioned in relation to the resulting failure? Was there any follow up action taken?Was there any plan to alleviate further problems?
Be critical in your assessment – sometimes the quality of the available source of informationcould be questionable (which is a typical downfall of many Web resources). Use at least twodifferent sources; they might offer various perspectives on the same problem. You may wishtoorganize your findings in a tabular format. Offer the most essential info; be concise. In your writing use the following template identifying failure description, nature of softwarefailure, testing efforts regarding failure, follow up action, and URL where the material was found. This is an example
Failure description Therac-25 Accidents
Eleven Therac-25s, radiation therapy machines, were installed: five inthe US and six in Canada. Six accidents involving massive overdoses
to patients occurred between 1985 and 1987. The accidents occurred when the high-energy electron-beamwas
activated without the target having been rotated into place; the
2 of 2machine’s software did not detect that this had occurred, and did not
therefore determine that the patient was receiving a potentially lethal
dose of radiation, or prevent this from occurring. The very high
energy electron-beam directly struck the patients causing the feeling
of an intense electric shock and the occurrence of thermal and
radiation burns. In some cases, the injured patients died later fromradiation poisoning. Nature of software failure Several features of the Therac-25 are important in understanding the
accidents. Some of essential causes were:
(1) The engineers had reused software from older models. These
models had hardware interlocks that masked their software defects. Those hardware safety mechanisms had no way of reporting that theyhad been triggered, to at least indicate the existence of faulty software
commands
(2) The hardware provided no way for the software to verify that
sensors were working correctly
(3) The software was written in assembly language. While this was
more common at the time than it is today, assembly language is harder
to debug than most high-level languages. Any testing efforts
regarding the failure?
(1) Related problems were found in the Therac-20 software. These
were not recognized until after the Therac-25 accidents because the
Therac-20 included hardware safety interlocks and thus no injuries
resulted. (2) After the 2
nd
incident the Atomic Energy of Canada Limited
(AECL) sent a service technician to the Therac-25 machine. He was
unable to recreate the malfunction and therefore concluded that
nothing was wrong with the software. Some minor adjustments to the
hardware were made. Any follow up action taken?
Any plan to alleviate further
problems?
The machine was recalled in 1987 and the AECL made a variety of
changes in the software of the Therac-25 radiation treatment system. The machine itself is still in use today. URL (1) http://en.wikipedia.org/wiki/Therac-25
(2) The Therac-25 Accidents (PDF):
http://sunnyday.mit.edu/papers/therac.pdf
(3) An Investigation of the Therac-25 Accidents (IEEE Computer)
http://users.csc.calpoly.edu/~csturner/courses/300/Therac-25.pdf
Value 10 points
3.Consider a software system for an autonomous vehicle and in this context discuss the meaningof the pertinent software qualities (say, functionality, reliability, portability, efficiency, etc.). Name them and complete a quality risk analysis. Rate technical risks and business risks. Use a 5- point scale (1- very high, 2- high… 5- very low).
