Book Excerpt

Brownfield Development: An Agile Approach to a Waterfall Problem

The "Brownfield" application development lifecycle differs from that of the traditional waterfall method employed on large-scale developments and instead utilizes a more agile approach, write the authors of Eating the IT Elephant, in this sample book chapter.

Chapter 8: Brownfield Development

"The process of scientific discovery is, in effect, a continual flight from wonder." —Albert Einstein

Chapter Contents

Agile Waterfalls
The Brownfield Development Approach

The previous chapter discussed the methods and techniques that form the foundations of Brownfield. We investigated each of these and compared the differences and similarities. Brownfield was shown to have evolved from these methods.

This chapter shows how the Brownfield method is used within the project lifecycle. As in the previous chapter, the lifecycle approach has again evolved as a composite of a number of existing lifecycle approaches.

Excerpt from Eating the IT Elephant: Moving from Greenfield Development to Brownfield

By Richard Hopkins and Kevin Jenkins
Published by IBM Press
ISBN-10: 0-13-713012-0
ISBN-13: 978-0-13-713012-2

Agile Waterfalls

Large-scale development has traditionally been based around well-organized phases. Each phase is completed before moving on to the next phase and is defined through work breakdown structures, work product definitions, and quality criteria. When viewed on a plan, these phases form steps down the page; this picture has led to the term "waterfall development." The water moves in only one direction, filling each phase before moving on to the next phase.

The more complex projects get, the more rigorous the methods become—up to and including extensive use of static testing and formal systems engineering techniques. These techniques are used to form quality assurance checkpoints at key points along the waterfall.

Static testing consists of techniques such as inspections and design walkthroughs to test the system's requirements, design, and implementation before the system can be executed.

The checkpoints check progress and create rigorous, strong baselines. The baselines are made up of a single set of unambiguous, formally signed-off documents. Figure 8.1 shows these project phases together with the quality assurance checkpoints used to enforce the rigor. The example shown uses the baselines defined in Carnegie Mellon's Software Engineering Institute's Capability Maturity Model Integration (CMMI).

Figure 8.1: The major phases of the waterfall lifecycle are punctuated by formal gates that allow baselines (often commercial ones) to be defined.

On very large projects, many people have tried to shortcut this process (deliberately or through ineptitude, or both), and many have come unstuck.

As Barry Boehm and Richard Turner point out in their book, Balancing Agility and Discipline: A Guide for the Perplexed, five factors determine whether waterfall or agile methods will prevail on any particular project. For the purposes of this book, we have rephrased them, but we have stayed true to the spirit of their findings (see Table 8.1).

Table 8.1 Comparison of Agile and Waterfall Methods

Factor	Agile Characteristics	Waterfall Characteristics
Size	Optimal for small projects and teams; reliance on tacit knowledge	Tailored for large projects and teams
Mission-critical projects	Untested; general lack of documentation	Long history of use in such implementations
Stability and complexity of existing	Continuous refactoring used; suitable for dynamic and simple environments (typically Greenfield)	Structured baselines used; suitable for more static and complex environments environment (typically Brownfield)
Skills	Continuous involvement of highly skilled individuals; difficult to cope with many lower skilled resources	Highly skilled individuals needed in early phases; designed to cope with many lower-skilled resources in later phases
Suitable organization culture	Chaotic; dynamic; empowered	Roles well defined; procedures in place

As you can see, agile and waterfall development each have their strengths and drawbacks. To recast the comparison, it is both possible and safe to build a paper airplane without a detailed plan. It would be foolish to spend 20 minutes writing the instructions and then spend 20 seconds building the plane. However, building a passenger airliner without detailed, upfront design would be a long and expensive process involving a lot of rework that you would otherwise have avoided. (You'd also probably face a shortage of test pilots to take the airliner on its maiden flight.) Figure 8.2 summarizes the different development techniques used in building a paper airplane and building an airliner.

Figure 8.2: The development techniques used for a paper airplane and an airliner should be quite different.

In formal waterfall methods, defects are detected as early as possible through static and then executable testing. If defects are found, changes are made to the requirements, specifications, or solution design documents. Changes can ripple forward from the first work product affected to the last. This approach reduces the overall number of defects and is far more cost-effective than not following these best practices because it reduces the number of surprises and the amount of rework.