This relationship between three requirements levels is vital to the project's success.
Functional requirements are short statements that the product development team will use to build the software. They should be clear and unambiguous. For instance, "Passengers should be able to choose the preferred seat on the flight when booking plane tickets."
System and functional requirements crystallize into features
. Every feature meets the user's needs and fits business goals. Features can address multiple user and functional requirements. However, the desired list of features does not always align with the user's needs and requires extra work to ensure the bells and whistles do not replace vital features. Feature examples include browser bookmarks, automatic updates, or a spellchecker. External interface requirements
explain how the system should interface with users, hardware, or other software solutions. This set of requirements may include synchronization and third-party integration needs, as well as compatibility requirements. With the increasing number of products on the market, external interface requirements become more crucial to the project's success. Constraints
limit the developers' freedom during the design and development process. They may include preferred technologies or languages, legacy system limitations, architecture or documentation limitations, and more. Still, an unmanageable number of constraints can overcomplicate the development process, increase time and budget requirements, and make the whole project unviable.
After completing this level, business analysts like me can put together a system requirements specification
that becomes the go-to document for project managers, software engineers, QA specialists, and other members of the development team as well as other stakeholders.