Agility Guide

On some occasions, the nonfunctional aspects of the product are the prime reason for doing the project. If the users find the existing product difficult to use, slow, or unreliable, then the usability, performance, and reliability requirements could be considered the most important requirements for the new product. Paradoxically, these nonfunctional requirements are often overlooked, and sometimes this neglect leads to the downfall of the project.

Some, though not all, of the nonfunctional requirements should be the earliest to be gathered and understood. They should never be assumed, as frequently happens, even when the customers and the developers feel they are obvious.

Rabbit projects should use the requirements specification template (see appendix B) as a checklist of nonfunctional requirements types. Go through the list (make sure you also check the subtypes) with your key stakeholders and determine which properties are their highest priorities. "All of them" is not an acceptable answer. Keep the project team aware of these high-priority requirements as you work through the use cases.

Horse projects have multiple stakeholders. For this reason, the requirements analysts usually need to take care that they capture the nonfunctional requirements, as well as identify and deal with the conflicts between requirements originating from the different and scattered stakeholders. Horse projects should investigate all the nonfunctional types and their applicability to the product and look for conflicting requirements early.

Elephant projects need to capture all of the requirements in written form, including the nonfunctional ones. This entire chapter is relevant for elephant projects. We suggest you group the nonfunctional requirements by type in the specification (see the requirements specification template in appendix B). Requirements can be grouped by use case, but as a certain amount of overlap between use cases is common, grouping by type helps prevent duplication.