- The Requirements Process in Context
- A Case Study
- Project Blastoff
- Trawling for Requirements
- Quick and Dirty Modeling
- Writing the Requirements
- Quality Gateway
- Reusing Requirements
- Reviewing the Requirements
- Iterative and Incremental Processes
- Requirements Retrospective
- Evolution of Requirements
- The Template
- The Snow Card
- Your Own Requirements Process
- Formality Guide
- The Rest of This Book
Writing the Requirements
A major problem in system development is misunderstood requirements. To avoid any misunderstanding, the analysts must write their requirements in an unambiguous and testable manner, and at the same time ensure that the originating stakeholder understands and agrees with the written requirement before it is passed on to the developers. In other words, the analysts write the requirements so as to ensure that parties at either end of the development spectrum are able to have an identical understanding of what is needed.
Although the task of writing down the requirements might seem an onerous burden, we have found it to be the most effective way to ensure that the essence of the requirement has been captured and communicated, and that the delivered product can be tested. (See Figure 2.5.)
Figure 2.5. The requirements are captured in written form to facilitate communication between the stakeholders, the analysts, and the developers (and anyone else who has an interest). By writing the requirements carefully, the team ensures that the correct product is built.
The IceBreaker analysts start by writing their requirements using business language so that the nontechnical stakeholders can understand them and verify their correctness. They add a rationale to the requirements—it shows the background reason for the requirement, which removes much of the ambiguity. Further, to ensure complete precision and to confirm that the product designers and developers can build exactly what the stakeholder needs, they write a fit criterion for each requirement. A fit criterion quantifies, or measures, the requirement, which makes it testable, which in turn allows the testers to determine whether an implementation meets—in other words, fits—the requirement.
The rationale and the fit criterion make the requirement more understandable for the business stakeholder, who has on several occasions said, “I am not going to have any requirements that I do not understand, nor will I have any that are not useful or that don’t contribute to my work. I want to understand the contributions that they make. That’s why I want each one to be both justified and measurable.”
The business analyst has a different, but complementary, reason for measuring requirements: “I need to ensure that each requirement is unambiguous; that is, it must have the same meaning to both the stakeholder who originated it and the developer who will build it. I also need to measure the requirement against the stakeholder’s expectations. If I can’t put a measurement to it, then I can never tell if we are building the product the stakeholder really needs.”
The analysts use two devices to make it easier to write their specification. The first device, the requirements specification template, is an outline and guide to writing a requirements specification. The business analysts use it as a checklist of the requirements they should be asking for, and as a consistent way of organizing their requirements documents. The second device is a shell, also known as a snow card. Each atomic (that’s the lowest level) requirement is made up of a number of attributes, and the snow card is a convenient layout for ensuring that each requirement has the correct constituents.
Of course, the writing process is not really a separate activity. In reality, it is integrated with the activities that surround it—trawling, prototyping, and the quality gateway. However, for the purposes of understanding what is involved in putting the correct requirements into a communicable form, we will look at it separately.
Iterative development methods employ user stories as a way of conveying the requirements. The stories are, in fact, placeholders for lower-level requirements; they are augmented during conversations between the developers and the stakeholders to flush out the detailed requirements. In Chapter 14, Requirements and Iterative Development, we look closely at how the business analyst can produce better user stories. Working iteratively does not obviate the need for requirements, but rather seeks to discover and communicate the requirements in a different manner.
The primary reason for wanting written requirements is not to have written requirements (although that is often necessary), but rather to write them. Writing the requirement, together with its associated rationale and fit criterion, clarifies it in the writer’s mind, and sets it down in an unambiguous and verifiable manner. To put that another way, if the business analyst cannot correctly write the requirement, he has not yet understood it.