Software ects of Strategic Defense Systems

Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Software Aspects of Strategic Defense Systems,Team Turkey,Joe,Kim,Senthil,Smitha,President Reagans SDI,In March 1983,President Reagan called for a “Strategic Defense Initiative”(SDI).,“I call upon the scientific community to give us the means of rendering these nuclear weapons impotent and obsolete.”,The SDI program came to be popularly called “Star Wars.”,Parnas Background,Doesnt object to weapons development in general,8yrs experience working on military aircraft,20yrs in the software engineering field,June 28,1985-Parnas resigns from the,$1,000/day,panel,Reasons for resignation,Software is unreliable,Unattainable goal due to SDI properties,Software techniques inadequate,SE improvements will be insufficient,AI and Automatic Programming wont help,Problems with Proofs,Research is inefficient and ineffective,Software is Unreliable,Software often produced with“bugs”,Problems persist for several versions and sometimes worsen with upgrades,Digital computers have large#of states but made from redundant subsystems(which can be exhaustively tested,but the,whole system,ca,n,t),#of p,ossible states too high in Software,Functions describing their behavior not continuous and cant be mathematically verified,L,ogical expressions often harder to understand than the program itself,Most Programmers dont,know the tools of the trade,Cant Trust that SDI Character,Target and decoys have unknown characteristics,(need to identify,track,and direct weapons towards them),Fatal errors,will occur,if developed without knowledge of characteristics or with characteristics that can be changed by an attacker on day of battle,Attackers countermeasures make network of sensors and weapons unreliable,Fail-soft only successful when:failures predicted from past history,component failures unlikely and statically independent,system has excess capacity,real-time deadlines can be missed,None true for,SDI,system,Impossible to test under real conditions,No faith without extensive tests,Most massive,costly software ever attempted,Service period too short for humans to debug and modify programs,Debuggers notes on army truck in Vietnam not possible in 30-90 minute war,Real-time computation deadlines,worst case amount of resources cant be predicted,Efficiency and predictability require some,preruntime,scheduling,need worse case real-time schedule,Large variety of sensors and weapons each requiring complex software,suite will grow during development and after deployment(subject to independent modification),Difficulties increase with:size of the system,#of independent subsystems,and#of interfaces,One Shot at the Title,Flow chart,approach,“think like a computer”,I,mproved with larger steps,Leads to confusion as data has different meaning under different circumstances,Concurrency program appear to be doing more than one thing at a time,Multiprocessing program DOES more than one thing at a time,Yes,Professional Programmers use this,conventional,approach,Trial and Error software released when rate of finding new errors slows down,New SE Techniques,Research aimed at reducing amount of information needed to test and maintain,Structured programming and formal program semantics,Use of formally specified abstract interfaces(information hiding),Use of cooperating sequential processes,Gap between theory and practice,Good software engineering can be done,its just far from easy,It reduces,NOT ELIMINATES,errors thus,there is,still,a,need testing,Improvements in SE,New languages and environments will help but they are not a major impediment to our work.,AI makes big claims but can offer no help,Automatic Programming is just a euphemism for programming in a higher-level language.,Still need to specify an algorithm,N,o breakthroughs,The fault lies not in our tools but in ourselves and in the nature of our product.,Artificial Flowers and Intelligence,AI-1-,S,olving problems,which previously could only be done with human intelligence,This definition changes over time,Best work in this area makes no attempt to mimic peoples problem solving techniques,Mostly problem specific,requires abstraction and creativity to transfer the work,AI-2-Heuristic or Rule Based Programming/Expert Systems,Approach is dangerous and misleading,Rules obtained are inconsistent,incomplete,and inaccurate,Evolutionary approach results in poorly understood behavior which is hard to predict,Spectacular behavior on small#of obvious cases,Prove it,Cant use e,xhaustive case analysis,No p,rolonged,realistic,testing,Use,Mathematical analysis,Dont have exact specifications to which one can apply a proof,Proofs themselves may contain errors,Concurrency adds difficulty to proofs,No techniques to prove programs robust enough to operate with unknown hardware failures or input errors,Getting what youve paid for,Those who make purchasing decisions dont know what theyre buying,Most difficult and crucia