The process of kanban, associated with the Toyota production system, incorporates the Japanese philosophy of Muda. Muda is the avoidance or elimination of waste and removing useless activities that do not provide value to the customer. The kanban process was developed by Taiichi Ohno to provide the Toyota production system with a practical approach to specific production and market conditions and to maintain a smooth production flow to promote continuous improvement. Kanban is a Japanese expression meaning signboard and was designed as a flow control system in manufacturing in which downstream process demand signals trigger upstream process activities. Although developed for the manufacturing sector to reduce waste in product production, the Kanban philosophy has been applied to software development activities.
Kanban includes a visual workflow on a board divided into columns. Teams use a Kanban board to visualize work progress to facilitate product improvements, monitoring of processes, and effective workflow management. The Kanban board aims to improve the workflow by supporting the principles of limiting work in progress, creating value throughout the process, increasing throughput, and embedding quality within the process. Additionally, kanban boards provide a process to manage the workflow, balance throughput, and make processes explicit as work moves through the different states. Each state in the Kanban process has a clearly defined entry and exit point, providing the team and management with a visual representation of progress.
Work requests are defined in the Kanban backlog to identify the work items the team needs to accomplish. In software development, stakeholders prioritize the importance, urgency, or value requests. Features or requests are selected and placed on the board. Each column on the Kanban board limits the amount of work in progress within the column or lane. Based on prioritization, work items are pulled through the workflow using defined stages such as “to do,” “in progress,” and “done.” Work items are tasks pulled only when required. Each stage limits the number of items (work in progress) to avoid the potential for bottlenecks. Limiting work in progress restricts the number of ongoing activities to avoid an excess of initiated tasks and unfinished work. The Kanban method allows a team to respond to market changes, reduce waste, increase quality, and improve predictability.