Breaking Down the Work is Essential

WHAT: In another section, we describe the Product Backlog as a "constantly evolving artifact" that is never complete. Product Backlog Refinement is the work that is done to constantly evolve the Product Backlog.

Most Product Backlogs were at some point an unsorted collection of ideas for features, enhancements, improvements, and capabilities for a Product. To provide transparency and focus, the Product Owner collaborates with other members of the Scrum Team to refine those ideas, adding details, estimates, and an order to each item. They also ensure that any single Product Backlog Item that is likely to be pulled into the next Sprint is small enough to reasonably reach the definition of done within the Sprint time-box. Once the items at the top of the ordered Product Backlog have these characteristics, they are considered "Ready" for Sprint Planning. While it is possible to go through Product Backlog Refinement for every known item in the Product Backlog, the focus is usually on just enough Product Backlog Items to fill the next Sprint or two. This "just in time" Product Backlog Refinement eliminates the waste that is possible when trying to provide clarity and detail for every known item long before it is pulled into a Sprint.

WHO: The Product Owner and Development Team collaboratively refine the Product Backlog. However, Product Backlog items can be updated at any time by the Product Owner or at the Product Owner's discretion. The Development Team is responsible for providing estimates.

WHEN: Product Backlog Refinement is an ongoing activity throughout the life of a Product Backlog. Since there is no gap between Sprints, Product Backlog Refinement occurs during Sprints and usually consumes no more than 10% of the capacity of the Development Team. Scrum does not define a particular event, process, or timebox for Product Backlog Refinement, so the Scrum Team decides how and when refinement is done.