Product Backlog Items
Each PBI represents work that the team intends to do. There is no rule about what information each PBI should contain, how it’s written or formatted, the granularity of each PBI or the tools used to maintain the Product Backlog.
PBIs are written in the form that serves the team best. For example, they can be written as user stories, hypotheses, defect reports or whatever other format helps the team. They generally contain a title, description, a size estimation and an estimation of value.
PBIs may describe new functionality; improvements to existing functionality; a problem with the current product that must be addressed; non-functional requirements for the product (such as reliability standards); new ideas; experiments, etc. They can be anything, as long as they help the team understand what it needs to do.
PBIs are written at the right level of detail needed by the Developers at the time. When first created, they may be very high-level and may only act as a placeholder. Over time, as more information is uncovered or as they become more important to address, they are improved and refined. Eventually they will have sufficient information for Developers to take action.
The Product Owner is accountable for creating PBIs. They can delegate the responsibility so that anyone on the team may add PBIs to the backlog.
The size estimations are done by the Developers because they are the only ones in a position to estimate how much work each PBI involves. There are many ways to estimate the size of PBIs:
- Absolute - often time-based; for example, “This PBI will take 9 hours of work”.
- Relative - uses a scale that lets developers estimate the size of the PBIs relative to each other; for example, story points or t-shirt sizing.
- Flow metrics - based on the team’s historical data such as throughput
- Right sizing - identifies items that are small enough to be completed within one single Sprint, often using a flow-based approach; for example, Developers discuss if they can complete a PBI according to their Definition of Done comfortably within one Sprint, otherwise they should break down the PBI
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