The Scrum framework consists of five events, three artifacts and three accountabilities. These events, artifacts and accountabilities provide a framework within which teams work together to deliver value.
The Product Backlog is an important artifact in Scrum. The Product Backlog is a single source of requirements and work for the Scrum team. Refinement of the Product Backlog is the act if adding detail, order and size to items in the Product Backlog.
Refinement is an important activity for the Scrum Team. So, why isn't Refinement considered a formal Scrum event? The key lies in the nature of the activity. Refinement is an ongoing, adaptive process that doesn't have a fixed time frame like the other Scrum events. It's more about preparing for the future sprints rather than focusing on the current increment being delivered.
Refinement
During Refinement, the Product Owner may work together with Developers and Stakeholders to brainstorm ways to add value to the Product. Refinement can take place in meetings with the Scrum team or in one-on-one meetings with Stakeholders, customers or others who have an interest in the success of the Product. The purpose of Refinement is create an ordered Product Backlog that shows what the Scrum team will work on next, where the highest ordered Product Backlog items are sized such that they can be completed within one Sprint.
This process is not time boxed because the Product Owner may invest more time or less time in refining the Product Backlog depending upon the needs of the Product. For new Products with low trust, the Product Owner may need to invest more time in Refinement to convince a source of funding to invest in the Product. For existing Products with high trust, the Product Owner may have just enough ready work for the next Sprint.
Scaling with Nexus and Refinement
When there are three or more Scrum teams working together to support a single Product, sometimes the teams may decide to adopt the Nexus scaling framework to help them manage dependencies and optimize value delivery across multiple Scrum teams. The Nexus framework takes into account that when several Scrum teams are working together, Refinement is a shared activity. For this reason, Nexus is a formal event in the Nexus framework. While it is still not time boxed, Refinement takes on a more structured form and becomes a formal event.
Conclusion
Refinement an important activity for Scrum Teams, even though it's not considered a formal event in the traditional Scrum framework. It's an ongoing activity that helps ensure the Product Backlog is well-prepared for future Sprints. When teams scale value delivery using the Nexus framework, Refinement becomes a formal event to facilitate coordination across multiple Scrum teams.
While Refinement may not be listed as a formal event in Scrum, its importance cannot be overstated. It serves as the foundation for effective Sprint Planning and contributes significantly to the success of each Sprint.