If developers and testers are not engaged in designing the specifications, those specifications have to be separately communicated to the team. In practice, this leaves a lot of opportunities for misunderstanding and details being lost in translation. As a consequence, business users have to validate the software after delivery, and teams have to go back to change it if it fails validation. This is all unnecessary rework.
Instead of relying on any single person to get the specifications right in isolation, successful delivery teams engage in specifying the solution collaboratively with the business users. People coming from different backgrounds use different heuristics to solve problems and have different ideas. Technical experts know how the underlying infrastructure can be used better, or how emerging technologies can be applied. Testers know how the system is likely to break or where to look for potential issues, and these issues should be prevented from occurring in the first place. All this information needs to be captured as the specification of work.
Specifying Collaboratively enables us to harness the knowledge and experience of the whole team. It also creates a collective ownership of specifications, making everyone much more engaged in the delivery process.
