SE401 · Annotated SlidesSoftware Quality — Software Quality
Software Quality · Annotated slides

Software Quality

Factors in project success and failure (Chaos report), the HealthCare.gov launch case study, reliability metrics (MTTF, MTTR, MTBF, availability), the spectrum of quality attributes (correctness, reliability, robustness, safety…), the cost of quality and of defects, verification and validation, the V-model and the levels of testing.

Slide text Study notes Highlight: key words Tips, tricks & traps Seen again elsewhere How it can come up
Slide 1: Slide 1
Exam weight Low
    Slide 2: • ƒ –‘”•‹”‘Œ‡ –— ‡•• ƒ‹Ž—”‡
    Exam weight Low
      Slide 3: Slide 3
      Exam weight Low
        Slide 4: • ƒ›•‘ˆ–™ƒ”‡”‡Žƒ–‡†ˆƒ‹Ž—”‡•ƒ—–‘’‹Ž‘–•›•–‡•ƒ‹”–”ƒˆˆ‹  ‘–”‘Ž•›•–‡• „ƒ‹‰•›•–‡• 
        Exam weight Low
          Slide 5: ‘ˆ–™ƒ”‡”‘Œ‡ –•Šƒ˜‡ƒ–‡””‹„Ž‡–”ƒ ”‡ ‘”†
          Exam weight Low
            Slide 6: ”‘Œ‡ –— ‡•• ›’‡Š‡’”‘Œ‡ –‹• ‘’Ž‡–‡†‘–‹‡ƒ†‘„—†‰‡– ™‹–ŠƒŽŽˆ‡ƒ–—”‡•ƒ†ˆ— –‹‘•ƒ•‹‹–‹ƒŽŽ›•’‡ ‹ˆ‹‡† 
            Exam weight Low
            1. Chaos report: only a minority of projects succeed (on time, on budget, full scope); the rest are challenged or fail.
            Slide 7: Slide 7
            Exam weight Low
              Slide 8: ƒ•‡–—†› Š‡ ‹–‹ƒŽƒ— Š‘ˆ ‡ƒŽ–Šƒ”‡‰‘˜
              Exam weight Low
                Slide 9: Slide 9
                Exam weight High
                1. HealthCare.gov (2013): ~$500M+, crashed at launch: changing requirements, late and inadequate testing (no end-to-end test until days before launch), poor management.
                🎯 How this can come up · 1 question
                Written

                Name two software-engineering failures behind the HealthCare.gov launch.

                Slide 10: • ‡”ˆ‘”ƒ ‡”‡•’‘•‡–‹‡Žƒ†‹‰’ƒ‰‡•
                Exam weight Low
                  Slide 11: Slide 11
                  Exam weight Low
                    Slide 12: Slide 12
                    Exam weight Low
                      Slide 13: • ˜‘Ž˜‹‰‘ŽŽ‹‰‡“—‹”‡‡–•
                      Exam weight Low
                        Slide 14: Slide 14
                        Exam weight Low
                          Slide 15: • ƒƒ‰‡‡–‡š’‡”–‹•‡‹•‹‰‡––‹‰ ‘–”ƒ –•‘–†‡Ž‹˜‡”‹‰ ’”‘Œ‡ –•
                          Exam weight Low
                            Slide 16: • ‘˜‡”‡– ’”‘Œ‡ –•
                            Exam weight Low
                              Slide 17: • „—‰ˆ‹š‡•„›–Š‡‡†‘ˆ‘˜
                              Exam weight Low
                                Slide 18: • ••—‡•‘†ƒ–ƒƒ —”ƒ ›ƒ† ‘’Ž‡–‡‡••
                                Exam weight Low
                                  Slide 19: •  ‡–—”‡ –‘‘‘˜‡”‹ ƒƒ•–Š‡Ž‡ƒ† ‘–”ƒ –‘”ˆ‘”†‡˜‡Ž‘’‡– ƒ†ƒ‹–‡ƒ ‡
                                  Exam weight Low
                                    Slide 20: • ”‘ŽŽ‡–ˆ‘”•–ƒ–‡•
                                    Exam weight Low
                                      Slide 21: • †‘’–•‘ˆ–™ƒ”‡‡‰‹‡‡”‹‰„‡•–’”ƒ –‹ ‡•
                                      Exam weight Low
                                        Slide 22: Slide 22
                                        Exam weight Low
                                          Slide 23: • ‡”ˆ‘”ƒ ‡
                                          Exam weight Low
                                            Slide 24: • ™‘‡›‡–”‹ •ˆ‘”‹–”‹•‹ ’”‘†— –“—ƒŽ‹–›ƒ”‡‡ƒ‹‡‘ ƒ‹Ž—”‡  ƒ†ƒ˜ƒ‹Žƒ„‹Ž‹–›
                                            Exam weight Low
                                            1. MTTF: mean time to failure. MTTR: mean time to repair. MTBF = MTTF + MTTR.
                                            Slide 25: • ‡ƒ–‹‡„‡–™‡‡ˆƒ‹Ž—”‡•
                                            Exam weight High
                                            1. Availability = MTTF / (MTTF + MTTR) × 100%.
                                            🎯 How this can come up · 1 question
                                            MCQ

                                            MTTF = 98 hours, MTTR = 2 hours. Availability =

                                            Slide 26: • ˜ƒ‹Žƒ„‹Ž‹–›
                                            Exam weight Low
                                              Slide 27: • ‘ˆ–™ƒ”‡ƒ˜ƒ‹Žƒ„‹Ž‹–›‹•–Š‡’”‘„ƒ„‹Ž‹–›–Šƒ–ƒ’”‘‰”ƒ‹•‘’‡”ƒ–‹‰ ƒ ‘”†‹‰–‘”‡“—‹”‡‡–•ƒ–ƒ‰‹˜‡’‘‹–‹–‹‡ƒ†‹•†‡ˆ‹‡†ƒ•
                                              Exam weight Low
                                              1. "Five nines" (99.999%) availability ≈ 5 minutes of downtime a year.
                                              Slide 28: • ‡Ž‹ƒ„‹Ž‹–›†‡’‡†•‘–Š‡ —‹– ‘ˆ‘’‡”ƒ–‹‘
                                              Exam weight Low
                                                Slide 29: • –‡‰”ƒ–‹‘–‡•–‹‰
                                                Exam weight Low
                                                  Slide 30: •  ‡’–ƒ ‡–‡•–‹‰
                                                  Exam weight Low
                                                    Slide 31: Slide 31
                                                    Exam weight Low
                                                      Slide 32: ‘‡’‘••‹„Ž‡†‡ˆ‹‹–‹‘• • —ƒŽ‹–›œ‡”‘†‡ˆ‡ –•”‘•„›
                                                      Exam weight Low
                                                        Slide 33: ‘ˆ–™ƒ”‡›•–‡—ƒŽ‹–‹‡•
                                                        Exam weight Low
                                                        1. Qualities: correctness, reliability, robustness, safety, performance, usability, security, maintainability, reusability, portability, interoperability.
                                                        Slide 34: • ‘””‡ –‡••
                                                        Exam weight Low
                                                        1. Correctness: consistent with the specification (all or nothing). Reliability: probability of operating without failure under a usage profile (statistical).
                                                        Slide 35: • ƒˆ‡–›
                                                        Exam weight High
                                                        1. Safety: prevents undesirable behaviours (hazards). Robustness: behaves reasonably (degrades gracefully) outside normal conditions.
                                                        🎯 How this can come up · 1 question
                                                        MCQ

                                                        A system that keeps working in a degraded mode when the network fails is:

                                                        Slide 36: • ‘””‡ –‡••‹•ƒƒŽŽ‘”‘–Š‹‰’”‘’‘•‹–‹‘
                                                        Exam weight Low
                                                          Slide 37: • ˆ‘”ƒŽŽ›•‘ˆ–™ƒ”‡‹•”‡Ž‹ƒ„Ž‡‹ˆ–Š‡—•‡” ƒ†‡’‡†‘‹–Š‡ •’‡ ‹ƒŽ‹œ‡†Ž‹–‡”ƒ–—”‡‘•‘ˆ–™ƒ”‡”‡Ž‹ƒ„‹Ž‹–›†‡ˆ‹‡•”‡Ž‹ƒ„‹Ž‹–›‹–‡”•
                                                          Exam weight Low
                                                            Slide 38: • ’”‘‰”ƒ‹•”‘„—•–‹ˆ‹–„‡Šƒ˜‡•”‡ƒ•‘ƒ„Ž›‡˜‡‹ ‹” —•–ƒ ‡•–Šƒ–™‡”‡‘–ƒ–‹ ‹’ƒ–‡†‹–Š‡
                                                            Exam weight Low
                                                              Slide 39: • ‘””‡ –‡••ƒ†”‡Ž‹ƒ„‹Ž‹–›ƒ”‡ ‘–‹‰‡–‘‘”ƒŽ‘’‡”ƒ–‹‰ ‘†‹–‹‘•
                                                              Exam weight Low
                                                                Slide 40: Slide 40
                                                                Exam weight Low
                                                                  Slide 41: SFMJBCMFCVU SPCVTUCVUOPU OPUDPSSFDU TBGFDBUBTUSPQIJD
                                                                  Exam weight Low
                                                                    Slide 42: Slide 42
                                                                    Exam weight Low
                                                                      Slide 43: • ‡”ˆ‘”ƒ ‡
                                                                      Exam weight Low
                                                                        Slide 44: • •ƒ„‹Ž‹–›
                                                                        Exam weight Low
                                                                          Slide 45: • ƒ‹–ƒ‹ƒ„‹Ž‹–›
                                                                          Exam weight Low
                                                                            Slide 46: Slide 46
                                                                            Exam weight Low
                                                                              Slide 47: • ‘”•‘ˆ–™ƒ”‡–™‘‹†•‘ˆ“—ƒŽ‹–›ƒ›„‡‡ ‘—–‡”‡†
                                                                              Exam weight Low
                                                                                Slide 48: • ”‡˜‡–‹‘ ‘•–•‹ Ž—†‡
                                                                                Exam weight Low
                                                                                1. Cost of quality: prevention (training, reviews) + appraisal (testing) + internal failure (rework before release) + external failure (after release: support, recalls).
                                                                                Slide 49: • Šƒ– ’ •™”‘‰™‹–Š ’‡”ˆ‘”ƒ ‡–‘ —•–‘‡”• ‡š’‡ –ƒ–‹‘• ”ƒ–Š‡”–Šƒ “ ’ ” ”‡“—‹”‡‡–•
                                                                                Exam weight Low
                                                                                  Slide 50: explains
                                                                                  Exam weight Low
                                                                                    Slide 51: • ‹’Ž‹•–‹ ƒŽŽ›•‘ˆ–™ƒ”‡’”‘†— –“—ƒŽ‹–›‹•Žƒ ‘ˆ “ „—‰• ‹–Š‡’”‘†— – ” • Š›‹•–Š‹•’”‘„Ž‡ƒ–‹ ƒŽˆ‘”•‘ˆ–™ƒ”‡•›•–‡•
                                                                                    Exam weight Low
                                                                                      Slide 52: Slide 52
                                                                                      Exam weight Low
                                                                                        Slide 53: • ˜‡‡š’‡”‹‡ ‡†•‘ˆ–™ƒ”‡‡‰‹‡‡”•‹Œ‡ –ƒ†‡ˆ‡ –ƒ„‘—–‡˜‡”›–‡Ž‹‡• ‘ˆ ‘†‡
                                                                                        Exam weight Low
                                                                                          Slide 54: Slide 54
                                                                                          Exam weight Low
                                                                                            Slide 55: Slide 55
                                                                                            Exam weight Low
                                                                                            1. The later a defect is found, the more it costs to fix (up to 100× after release).
                                                                                            Slide 56: Slide 56
                                                                                            Exam weight Low
                                                                                              Slide 57: Slide 57
                                                                                              Exam weight Low
                                                                                                Slide 58: Slide 58
                                                                                                Exam weight Low
                                                                                                  Slide 60: Slide 60
                                                                                                  Exam weight Low
                                                                                                    Slide 61: Slide 61
                                                                                                    Exam weight Low
                                                                                                      Slide 62: • ‡•–‹‰ ƒ„‡†‘‡ˆ‘”˜‡”‹ˆ‹ ƒ–‹‘ƒ†˜ƒŽ‹†ƒ–‹‘ • ‡”‹ˆ‹ ƒ–‹‘
                                                                                                      Exam weight Low
                                                                                                        Slide 63: Slide 63
                                                                                                        Exam weight Low
                                                                                                          Slide 64: • —ƒŽ‹–‹‡• ƒ‘–„‡ƒ††‡†ƒˆ–‡”†‡˜‡Ž‘’‡–
                                                                                                          Exam weight Low
                                                                                                            Slide 65: • —ƒŽ‹–›’”‘ ‡•••‡–‘ˆƒ –‹˜‹–‹‡•ƒ†”‡•’‘•‹„‹Ž‹–‹‡•
                                                                                                            Exam weight Low
                                                                                                              Slide 66: • ‘”‡˜‡”›†‡˜‡Ž‘’‡–ƒ –‹˜‹–›–Š‡”‡‹•ƒ ‘””‡•’‘†‹‰–‡•–‹‰ ƒ –‹˜‹–›
                                                                                                              Exam weight Low
                                                                                                                Slide 67: • ‹– ‘’‘‡–‘†—Ž‡–‡•–‹‰ • –‡‰”ƒ–‹‘–‡•–‹‰
                                                                                                                Exam weight Low
                                                                                                                  Slide 68:  –—ƒŽ‡‡†• ƒ† ‡Ž‹˜‡”‡†ƒ ƒ‰‡ •‡” ‡’–ƒ ‡Ž’Šƒ‡–ƒ‡•–• ‘•–”ƒ‹–•
                                                                                                                  Exam weight Low
                                                                                                                  1. V-model: user requirements ↔ acceptance test, system spec ↔ system test, design ↔ integration test, code ↔ unit test.
                                                                                                                  Slide 69: • ‡•–‹‰‘ˆ‹†‹˜‹†—ƒŽ•‘ˆ–™ƒ”‡—‹–‘†—Ž‡ ‘’‘‡–•
                                                                                                                  Exam weight Low
                                                                                                                    Slide 70: • ‡•–‹‰’‡”ˆ‘”‡†–‘‡š’‘•‡†‡ˆ‡ –•‹–Š‡ ‹–‡”ˆƒ ‡• ƒ†‹–Š‡ ‹–‡”ƒ –‹‘•„‡–™‡‡ ‹–‡‰”ƒ–‡† ‘’‘‡–•‘”•—„•›•–‡•
                                                                                                                    Exam weight Low
                                                                                                                      Slide 71: • •‡†™Š‡ƒŽƒ”‰‡ƒ‘—–‘ˆ–‡•–‹‰‹•‡‡†‡†ƒ†–Š‡ Šƒ‰‡•™Š‹Ž‡ •ƒŽŽ ƒƒˆˆ‡ –ƒ›’ƒ”–•‘ˆ–Š‡•›•–‡
                                                                                                                      Exam weight Low
                                                                                                                        Slide 72: • ‡•–‹‰‘ˆƒ‹–‡‰”ƒ–‡†•›•–‡–‘˜‡”‹ˆ›–Šƒ–‹–‡‡–•–Š‡ •’‡ ‹ˆ‹ ƒ–‹‘
                                                                                                                        Exam weight Low
                                                                                                                          Slide 73: • ‡•––Š‡™Š‘Ž‡•›•–‡–‘‡•—”‡–Šƒ–‹–‡‡–•–Š‡ ”‡“—‹”‡‡–• • ‘ —•‘ —•–‘‡”ƒ ‡’–ƒ ‡
                                                                                                                          Exam weight Low
                                                                                                                            Slide 74: •  ‡’–ƒ ‡–‡•–‹‰
                                                                                                                            Exam weight Low
                                                                                                                              Slide 75: • ƒ†‘•–ƒ–‹•–‹ ƒŽ–‡•–‹‰ • Ž’Šƒ–‡•–‹‰
                                                                                                                              Exam weight Low
                                                                                                                                Slide 76: • ƒ†‘–‡•–•–ƒ–‹•–‹ ƒŽ–‡•–
                                                                                                                                Exam weight Low
                                                                                                                                  Slide 77: • ‹—Žƒ–‡†‘’‡”ƒ–‹‘ƒŽ–‡•–‹‰ • ‡”ˆ‘”‡†„›’‡”•‘‡Ž ƒ –‹‰ƒ• ’‘–‡–‹ƒŽ—•‡”• —•–‘‡”•
                                                                                                                                  Exam weight Low
                                                                                                                                  1. Alpha testing: by potential users at the developer’s site (controlled). Beta: by real users in their own environment.
                                                                                                                                  Slide 78: • ’‡”ƒ–‹‘ƒŽ–‡•–‹‰–‘†‡–‡”‹‡™Š‡–Š‡”‘”‘–ƒ ‘’‘‡– ‘”•›•–‡•ƒ–‹•ˆ‹‡•–Š‡—•‡” —•–‘‡”‡‡†•ƒ†ˆ‹–•™‹–Š‹–Š‡
                                                                                                                                  Exam weight Low
                                                                                                                                    Slide 79: • ’‡ –”—‘ˆ•‘ˆ–™ƒ”‡“—ƒŽ‹–‹‡• • ‡–”‹ •‘ˆ“—ƒŽ‹–›ƒ––”‹„—–‡•
                                                                                                                                    Exam weight Low