Running a project with Agile or Scrum methodologies does not mean that it’s ‘OK’ to skip functional requirements. Once, there was a company that gave application mockups to its developers without providing any details about what the application was supposed to do.
It was left to the developers to guess what actions the application should perform, based on the mockups. As expected, this led to a lot of iterations and unnecessary exchanges between the business and the developer. Days (of work) were wasted, as the changing functional requirements were communicated verbally to the developer. When the application was ready to be tested, the requirements changed again, because there were former business users in the QA department.
Essentially, application requirements should consist of mockups (also known as wireframes), business rules, a functional description of what each button/link does, and a list of the fields with their types and lengths. Requirements should be completed and signed off by the business before development begins. It is best if requirements are completed in related screens, so that the architect gets a broad view of things and is able to guide the developers accordingly. [...]
To read the full post and add comments, please visit the SogetiLabs blog: Skipping Functional Requirements in Projects is a Costly Mistake