Transcript safety
Assignments Week 5 • Work on your paper / presentation topic – papers are due 20 February (Tuesday) for both sections! • Reading: Baase Chapter 5 (Intel. Property) – quiz sometime this week, open Journals • Do weekly journal entry – this is a continuing assignment • random review possible CSC 300, Winter 2001 1 5th week • Study Therac-25 case – get outside references for full story • Groups will advocate for particular party – on moral, ethical and/or legal grounds – produce a slide or two for 5 minute presentation • explicitly reference the SE Code of Ethics and moral or legal principles you want to use • each group member should participate – group presentation next week CSC 300, Winter 2001 2 Reliability and Safety • As usual, define the main terms – “reliability” – “safety” • a property of “software” itself? – what is a “system”? a “systems engineer”? – what is our relationship to it as software engineers? » what is “safety-critical” software? » what is “mission-critical” software? » examples? CSC 300, Winter 2001 3 Software Engineering Code • What is expected of a software “professional” (an ethical one :-) – list our duties under the code CSC 300, Winter 2001 4 What about Reality? • Software engineering strives for high quality and safety – Requirements issues • preciseness: formal specifications – what profit from the abstraction? • generality: usability by domain specialists – where is the right balance? CSC 300, Winter 2001 5 Formal Verification • Use mathematics to “solve” the problem – start from formal specification – prove the specification is • complete • consistent • correct – prove the implementation meets the specification CSC 300, Winter 2001 6 Limitations of the Formal Approach • Software verification depends on other software – multiple layer trust issues • Peer review is not possible – why not? • Implementation issues may not be addressed • What about the formal specification itself? CSC 300, Winter 2001 7 Testing Saves the Day? • Software Testing limitations – what is possible? – what is not? • But what is expected from the Software Engineering Ethics Code? CSC 300, Winter 2001 8 “Standards” for Software Reliability and Safety? • Can we agree on a “negligence” standard? – based on software “design” judgment • where we have some idea what to do – process issues • Are there other safety problems to be addressed? – what about “mistakes” • good design can’t prevent such things – pure product issues CSC 300, Winter 2001 9 How Does the Law Classify Product Defects? • Negligence standard for design defects – not criminal law - its only about money – “reasonability” “due care” “fault based” • when would society want to place the burden on the victim for accidents? – when the social value of the design is very high • when would society rather place the burden on the developer for accidents? – when the social value of the design is low CSC 300, Winter 2001 10 Legal Responsibility • Strict liability standard – “no fault” “cause based” “due care irrelevant” • when would society want to impose responsibility regardless of fault? – what accident costs should never be borne by a victim » does society (state of the art) ever benefit from a “mistake”? » developers must internalize these costs as a “cost of doing business” CSC 300, Winter 2001 11 Does this Defect Classification Apply to Software? • What is a “design” defect for software? • What is a “construction” mistake for the software product? • Can we tell the difference between them? – Really big cost consequences! CSC 300, Winter 2001 12 Ethics of the Issues • What are the ethics of personal injury cases? – list SE code provisions • what do they say? CSC 300, Winter 2001 13