While plan and development processes brought discipline to software development

While plan and development processes brought

This preview shows page 39 - 41 out of 517 pages.

While plan-and-development processes brought discipline to software development, there were still software projects that failed so disastrously that they live in infamy. Programmers have heard these sorry stories of the Ariane 5 rocket explosion , the Therac-25 lethal radiation overdose, and the FBI Virtual Case File project abandonment so frequently that they are clichés. No software engineer would want these projects on their résumés. Ariane 5 flight 501. On June 4, 1996, an overflow occurred 37 seconds after liftoff in a guidance system, with spectacular consequences ,
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when a floating point number was converted to a shorter integer. This exception could not occur on the slower Ariane 4 rocket, so reusing successful components without thorough system testing was expensive: satellites worth $370M were lost. One article even listed a “Software Wall of Shame” with dozens of highly-visible software projects that collectively were responsible for losses of $17B, with the majority of these projects abandoned ( Charettte 2005 ). Figure 1.4 summarizes four surveys of software projects. With just 10% to 16% on time and on budget, more projects were cancelled or abandoned than met their mark. A closer look at the 13% success of survey b) is even more sobering, as fewer than 1% of new development projects met their schedules and budgets. Although the first three surveys are 10 to 25 years old, survey d) is from 2013. Nearly 40% of these large projects were cancelled or abandoned, and 50% were late, over budget, and missing functionality. Using history as our guide, poor President Obama had only a one in ten chance that HealthCare.gov would have a successful debut. Agile is also known variously as a lightweight or undisciplined process. Perhaps the “Reformation moment” for software engineering was the Agile Manifesto in February 2001. A group of software developers met to develop a lighter-weight software lifecycle. Here is exactly what the Agile Alliance nailed to the door of the “Church of Plan and Document”: “We are uncovering better ways of developing software by doing it and helping others do it. Through this work we have come to value: Individuals and interactions over processes and tools Working software over comprehensive documentation Customer collaboration over contract negotiation Responding to change over following a plan That is, while there is value in the items on the right, we value the items on the left more.” Variants of Agile There are many variants of Agile software development ( Fowler 2005 ). The one we use in this book is Extreme Programming , which is abbreviated XP , and credited to Kent Beck. This alternative development model is based on embracing change as a fact of life: developers should continuously refine a working but incomplete prototype until the customer is happy with the result. In addition the customer should offer feedback on each iteration. Agile emphasizes test-driven development (TDD) to reduce mistakes by writing the tests before writing the code, user stories to reach agreement and validate customer requirements, and
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  • Spring '19
  • Dr.Marcos

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