During the iteration process, validation should occur as each unit of work is complete. At the end of every iteration the engineering team produces an artifact that can be demonstrated to the business owners. This demonstration can be conducted through a formal Business Iteration Planning Meeting (BIPM) or as part of a more informal process like a conference call or even a link to a demo instance of the application. User acceptance is a process that reoccurs throughout the life of the project at the end of each iteration. This looping process (see 6.1) is what allows the engineering team to validate the direction of the project and receive new instruction. More importantly it allows the team to "fail fast" and course correct to the expectations of business owners.
Ideas
Learn
Build