If you are still using a Work Breakdown Structure (WBS), then you still have the waterfall mindset: task driven.
Lean Agile mindset, however, is Value driven. Things of value are planned and delivered in Stories, not in tasks. Stories are chunked together in a meaningful Feature of value. Features are spread out into a quarterly (chunk of three months spread over a year length) roadmap. Stories spread out into two-week sprints.
In Lean Agile, WBS is out… Roadmap is in!
Product Managers…if someone is asking you to deliver a project plan in WBS format … and you are in the middle of a Lean Agile Transformation… then give him/her a roadmap of your Features (with milestones, risks, and dependencies) instead.
