Requirements Gathering using Object- Oriented Models

Transcription

1 Requirements Gathering using Object- Oriented Models Quality Assurance introduction What is Quality? Quality is defined as conformance to requirements Quality is not a measure of GOODNESS Phil B. Crosby, Quality is Free Program testing can be used to show the presence of bugs, but never to show their absence! Edsger W. Dijkstra You cannot control what you cannot measure. Tom DeMarco the job of the software engineer is to deliver high-quality software products at agreed cost and schedule even the most experienced software engineer injects about one defect for ten lines of code Watts S. Humphrey 1

2 Nine Possible Sources of Error 1. Poor understanding of needs 2. Poor definition of requirements 3. Communication issues between clients and developers 4. Design error (logical) 5. Programming Errors 6. Non-compliance with standards and standards 7. Insufficient testing 8. Interface Errors 9. Documentation Errors Importance of Software Quality Logiciel est une composante majeure des systèmes informatiques (environ 80% du coût total) utilisés pour: communication (ex. syst. téléphone, syst. de courriel); santé (surveillance); transport (ex. automobile, aéronautique); échanges économiques (ex. commerce électronique); divertissements; etc. Les défauts du logiciel sont extrêmement coûteux en terme de coût (d argent); de réputation; de perte de vie. 2

3 Importance of Software Quality The Mars Climate Orbiter (formerly the Mars Surveyor '98 Orbiter) was a 338-kilogram (745 lb) robotic space probe launched by NASA on December 11, 1998 to study the Martian climate, Martian atmosphere, and surface changes and to act as the communications relay in the Mars Surveyor '98 program for Mars Polar Lander. However, on September 23, 1999, communication with the spacecraft was lost as the spacecraft went into orbital insertion, due to ground-based computer software which produced output in non-si units of pound-seconds (lbf s) instead of the SI units of newton-seconds (N s) specified in the contract between NASA and Lockheed. The spacecraft encountered Mars on a trajectory that brought it too close to the planet, causing it to pass through the upper atmosphere and disintegrate. The cost of the mission was $327.6 million total for the orbiter and lander, comprising $193.1 million for spacecraft development, $91.7 million for launching it, and $42.8 million for mission operations. Importance of Software Quality Cluster was a constellation of four European Space Agency spacecraft which were launched on the maiden flight of the Ariane 5 rocket, Flight 501, and subsequently lost when that rocket failed to achieve orbit. The launch, which took place on Tuesday, 4 June 1996, ended in failure due to an error in the software design caused by assertions having been turned off, which in turn caused inadequate protection from integer overflow. This resulted in the rocket veering off its flight path 37 seconds after launch, beginning to disintegrate under high aerodynamic forces, and finally self-destructing by its automated flight termination system. The failure has become known as one of the most infamous and expensive software bugs in history. The failure resulted in a loss of more than US$370 million. 3

4 Importance of Software Quality 31.1% of projects canceled prior to completion. Cost $ 81 billion 52.7% of projects exceed budget. Cost $ 59 billion Large companies - delivered systems have roughly only 42% of the functions originally proposed SMEs - delivered systems have approximately only 74.2% of the originally proposed functions 4

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7 The definitions for these factors are: Executive Support: when an executive or group of executives agrees to provide both financial and emotional backing. The executive or executives will encourage and assist in the successful completion of the project. Emotional maturity is the collection of basic behaviors of how people work together. In any group, organization, or company it is both the sum of their skills and the weakest link that determine the level of emotional maturity. User Involvement: takes place when users are involved in the project decision-making and information-gathering process. This also includes user feedback, requirements review, basic research, prototyping, and other consensus-building tools. Optimization is a structured means of improving business effectiveness and optimizing a collection of many small projects or major requirements. Optimization starts with managing scope based on relative business value. Skilled staff are people who understand both the business and the technology. A skilled staff is highly proficient in the execution of the project s requirements and deliver of the project or product. SAME is Standard Architectural Management Environment. The Standish Group defines SAME as a consistent group of integrated practices, services, and products for developing, implementing, and operating software applications. Agile proficiency means that the agile team and the product owner are skilled in the agile process. Agile proficiency is the difference between good agile outcomes and bad agile outcomes. Modest execution is having a process with few moving parts, and those parts are automated and streamlined. Modest execution also means using project management tools sparingly and only a very few features. Project management expertise is the application of knowledge, skills, and techniques to project activities in order to meet or exceed stakeholder expectations and produce value for the organization. Clear Business Objectives is the understanding of all stakeholders and participants in the business purpose for executing the project. Clear Business Objectives could also mean the project is aligning to the organization s goals and strategy. 7

8 Software Quality Issues The uniqueness of the software product High complexity Product Invisibility Limited bug detection opportunities during the software development cycle Software Development Environments Under Contract Subject to Supplier Customer Relationship Requires Teamwork Requires cooperation and coordination with other development teams Requires interfaces with other systems Requires the continuation of the project as the team changes Requires maintenance for several years 8