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Iterative and Incremental Processes

One common misconception in the requirements world is that you have to gather all the requirements before moving on to the next step of design and construction. In other words, doing requirements means that you employ a traditional waterfall process. In some circumstances this is necessary, but not always. On the one hand, if you are outsourcing or if the requirements document forms the basis of a contract, then clearly you need to have a complete requirements specification. On the other hand, if the overall architecture is known, then construction and delivery can often begin before all the requirements are discovered. We show these two approaches in Figure 2.7, and suggest you consider which one works best for you when working on your own requirements projects. We also have a lot more to say on various approaches in Chapter 9, Strategies for Today’s Business Analyst.

Figure 2.7

Figure 2.7. Two (of many) variations on development life cycles. At the top of the figure is the traditional waterfall approach, in which the complete requirements document is put together before product development begins. At the bottom of the figure is an iterative process, in which, after a preliminary analysis, the product is developed in small increments. Both approaches achieve the same purpose.

On the IceBreaker project, the developers are ready to start building the product, so after the blastoff the key stakeholders select three (it could be any low number) of the highest-priority and greatest-value business use cases. The requirements analysts trawl and gather the requirements for only those business use cases, putting aside the rest of the work for now. Then, when the first tranche of requirements have successfully passed the quality gateway, the developers start their work. The intention is to implement a small number of use cases as early as possible to get the reaction of the stakeholders—if there are going to be any nasty surprises, the IceBreaker team wants to get them as early as possible. While the developers are building and delivering the first lot of business use cases, the analysts are working on the requirements for the next-highest-priority ones. Soon they have established a rhythm for delivery, with new use cases being implemented and delivered every few weeks.

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