The waterfall model is a traditional engineering approach applied to software engineering. A strict waterfall approach discourages revisiting and revising any prior phase once it is complete. This "inflexibility" in a pure waterfall model has been a source of criticism by supporters of other more "flexible" models. It has been widely blamed for several large-scale government projects running over budget, over time and sometimes failing to deliver on requirements due to the Big Design Up Front approach. Except when contractually required, the waterfall model has been largely superseded by more flexible and versatile methodologies developed specifically for software development. See Criticism of Waterfall model .
The Scrum Alliance has published a new whitepaper called “Coaching is Key for Scrum Success” which outlines some of the problems organizations face when implementing Scrum, how Scrum coaching can help, and what to look for in a Scrum coach. Most organizations run into issues when first implementing Scrum. Rather than let these problems continue to plague the Agile implementation and jeopardize the risk of success, many organizations find that working with a Scrum coach early in the process helps to avoid “Scrum-But” and reverting to old ways of doing things. Scrum coaches can also help to minimize learning curves, resolve organizational impediments and identify potential stumbling blocks early on. Scrum coaches help to streamline agile transformation by bringing an outside view of the organization to remove intrinsic bias and taking the time pressure off the product line managers by providing guidance and management of the Scrum implementation.