Chapter 3. Measure Twice, Cut Once: Upstream Prerequisites

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Contents

• Importance of Prerequisites page 24

• Determine the Kind of Software You're Working On page 31

• Problem-Definition Prerequisite page 36

• Requirements Prerequisite page 38

• Architecture Prerequisite page 43

• Amount of Time to Spend on Upstream Prerequisites page 55

Related Topics

• Key construction decisions: Chapter 4

• Effect of project size on construction and prerequisites: Chapter 27

• Relationship between quality goals and construction activities: Chapter 20

• Managing construction: Chapter 28

• Design: Chapter 5

Before beginning construction of a house, a builder reviews blueprints, checks that all permits have been obtained, and surveys the house's foundation. A builder prepares for building a skyscraper one way, a housing development a different way, and a dog-house a third way. No matter what the project, the preparation is tailored to the project's specific needs and done conscientiously before construction begins.

This chapter describes the work that must be done to prepare for software construction. As with building construction, much of the success or failure of the project has already been determined before construction begins. If the foundation hasn't been laid well or the planning is inadequate, the best you can do during construction is to keep damage to a minimum.

The carpenter's saying, "Measure twice, cut once" is highly relevant to the construction part of software development, which can account for as much as 65 percent of the total project costs. The worst software projects end up doing construction two or three times or more. Doing the most expensive part of the project twice is as bad an idea in software as it is in any other line of work.

Although this chapter lays the groundwork for successful software construction, it doesn't discuss construction directly. If you're feeling carnivorous or you're already well versed in the software-engineering life cycle, look for the construction meat beginning in Chapter 5, "Design in Construction." If you don't like the idea of prerequisites to construction, review Section 3.2, "Determine the Kind of Software You're Working On," to see how prerequisites apply to your situation, and then take a look at the data in Section 3.1, which describes the cost of not doing prerequisites.