【正文】 e acceleration pedal. Dom: The normal running of the motor is raised if and only if the acceleration pedal is pressed. SysReq: The handbrake shall be released if and only if the driver wants to start. The car?s air conditioner starts automatically, due to the car?s door being open, which resulted in the normal running of the motor being raised and the handbrake being released. 35 ./college/van lamsweerde : Setting the Scene 169。 2022 John Wiley and Sons Role and stakes of RE ? Technical impact – on many softwarerelated artefacts (as seen before, slide 24) ? Managerial impact – basis for munication among parties and for project management ? Legal impact – contractual mitment clientprovidersubcontractors ? Impact on certification – Mastered RE process required by many quality standards amp。 certification authorities 36 ./college/van lamsweerde : Setting the Scene 169。 2022 John Wiley and Sons Role and stakes of RE (2) ? Impact on economy, security, and safety – Cost and consequences of errors in requirements on the softwaretobe, assumptions about its environment ? Social impact – from user satisfaction to degradation of working conditions to system rejection 37 ./college/van lamsweerde : Setting the Scene 169。 2022 John Wiley and Sons Obstacles to good RE practice ? RE efforts often spent without guarantee of project contract being concluded ? Pressure on tight schedules, shortterm costs, catching up on technology ? Too little work available on RE economics – Lack of quantitative data on RE benefits amp。 cost savings – Progress in RE process is harder to measure than in design, implementation ? RDs are sometimes felt ... – big, plex, to be quickly outdated – too far away from the executable product customers are paying for 38 ./college/van lamsweerde : Setting the Scene 169。 2022 John Wiley and Sons Agile development and RE ? More agile development may overe some obstacles – early amp。 continuous provision of functionality of value to customer – by reducing the reqtocode distance ? Short RE cycles in spiral RE process, each directly followed by short implementation cycle – Useful functional increment is elicited directly from the user – Evaluation/spec/consolidation phases often shortcut (. spec = test case on the implementation) – Increment is implemented/tested by small team at same location, close to the user for instant feedback, using strict rules 39 ./college/van lamsweerde : Setting the Scene 169。 2022 John Wiley and Sons Strong assumptions for agility to be successful ? All stakeholder roles are reducible to one single role ? Project sufficiently small to be assignable to single, small, singlelocation team (programmers/testers/maintainers) ? “User” can interact promptly amp。 effectively ? Functionality can be provided quickly, consistently, incrementally from essential to less important (no prioritization required) ? Nonfunctional aspects, environment assumptions, objectives, alternative options, risks may receive little attention ? Little documentation required for work coordination amp。 product maintenance。 requirements precision not required。 verification before coding is less important than early release ? Requirements changes are not likely to require major code refactoring More/less agility is achievable by less/more weight in elicitation, evaluation, documentation, consolidation phases of RE cycles 40 ./college/van lamsweerde : Setting the Scene 169。 2022 John Wiley and Sons Setting the scene: summary ? What is Requirements Engineering? – RE is concerned with the problem world only – Scope: WHY, WHAT, WHO issues – Statement types: descriptive vs. prescriptive。 requirements, assumptions, domain properties, defs。 satisfaction arguments – Categories of requirements: functional, nonfunctional – RE is a spiral process。 elicitevaluatespecifyconsolidate cycles driven by corrections amp。 evolving needs – Multiple target qualities, defects to avoid some are critical ! – Weight on each RE phase may depend on project type – Requirements impact on many software artefacts ? Why engineer requirements? – Requirementsrelated errors are the most numerous, persistent, expensive, dangerous – Technical, managerial, legal, economical, social impact of RE ? Obstacles to good RE practice。 agility in spiral R