The most practical application of Scrum (i.e. the easiest to manage!) exists at the interface between those that own individual products and those that deliver the incremental enhancements to those products.
In a multi-purpose team environment (i.e. where the team delivering your predictable roadmap is also the team required to address live defects – BAU), it becomes more challenging to commit to a sprint of work (without interruption) because you can’t just leave a critical live defect… live …
[[flash back to Ken Schwaber‘s “A dead sheepdog is a useless sheepdog” quote (Agile Project Management with Scrum) – a sheepdog being a Scrum Master, a dead sheepdog being a Scrum Master that refuses to compromise Scrum law for the sake of principal without consideration for consequences… i.e. pick your fights.]]
The question: How do you balance predictability with flexibility in a way that minimises disruption (!?)
In this scenario, I like to combine Scrum with elements of Lean. Dedicate a percentage of your team velocity to quick-response tasks that can be managed in a Lean way (i.e. defined/delivered Just In Time) OR simply commit a percentage of your velocity to Stretch Tasks vs. Firm Goals. By planning for disruption but only taking the hit when/if it comes, business expectations are managed and the impact of change is minimised.
In this scenario, we continue to burn down on Firm Goals i.e. those comitted to at the beginning of the sprint but we burn up on everything else. This way we can measure the level of disruption occuring during a sprint and rationalise variations in team velocity.
Note that the above team anticipated a considerable amount of disruption in the sprint ahead so only comitted to delivering 65 points of their 100 point velocity.
The 35 points can either be made up of ‘Stretch task placeholders’ that will be delivered in order of priority should no other higher priority requirements arise OR can be filled by activities requiring immediate/quick response. In this situation the task is estimated by the team and they burn up on the points upon completion.
The higher the percentage of Firm Goals, the higher the team velocity i.e. less disruption = higher output. With that said, the higher output may not be of higher value… it’s about striking a balance.