Lean model

The Lean model applies the principles of lean manufacturing (originating from the Toyota Production System) to software and project development. Its central idea is to deliver maximum customer value with minimum waste. Mary and Tom Poppendieck adapted it to software as "Lean Software Development".

Seven principles of lean software development

1. Eliminate waste: remove anything that does not add value, such as unused features, extra documentation, waiting and task switching, defects, and handoffs.
2. Amplify learning: short feedback cycles, experiments, tests and reviews.
3. Decide as late as possible: keep options open until facts are known.
4. Deliver as fast as possible: short iterations give early feedback and value.
5. Empower the team: let people closest to the work make decisions.
6. Build integrity in: quality is built into the product through automated testing and continuous integration.
7. See the whole: optimise the whole system, not individual parts.

Types of waste (in software)

Tools

Value stream mapping, Kanban board, pull systems, continuous improvement (kaizen), 5 whys.

 Backlog -> [Doing] -> [Review] -> [Done]
 (Kanban: limit work in progress)

Advantages

Less waste, faster delivery, lower cost, better quality and satisfied customers.

Limitations

Needs a mature, disciplined team; less suitable for projects with fixed scope and heavy documentation needs.

Example: An IT support team uses a Kanban board and limits work in progress to three tickets per person. This reduces waiting and shortens resolution time.