Kanban

The Kanban method is another agile approach for modeling workflow processes. It is enjoying increasing popularity, especially in the area of IT, because it is easy to understand, easy to implement, and easily adapted to individual needs.

Kanban [3] is a term put together from the Japanese words "kan" (signal) and "ban" (card). It is the name of a principle that Taiichi Ohno used to organize the production processes at Toyota in 1947. He effectively oriented his concept on the central goals of lean manufacturing – namely, to reduce processing time, increase productivity, and create satisfaction and confidence.

Based on the insight that no method ever reaches perfection, the principle of continual improvement ("kaizen") also plays an important part in Kanban.

Pull and WIP

The core of the Kanban method is the pull system, in which the various stations in the process fill up their free capacity without external influence. At Toyota, signal cards (i.e., "Kanban") were used for this purpose, with which a station signaled that they had capacity available for processing the product of the previous station. The number of cards available corresponded to the total capacity of the respective station, so an overload could be ruled out. Thus the system introduced a work-in-progress (WIP) limit that was the decisive factor for the success of the Kanban principle.

An example that graphically demonstrates the pull system can be found in the Imperial Gardens in Tokyo. Upon entrance, each visitor is given a card with a request to return the card upon leaving the gardens. Entrance to the gardens is free, but it is only allowed as long as free cards are available. Because the cards are limited to a reasonable number, there can never be more visitors in the gardens than would allow for a pleasant stay.

Kanban has become known as an organizational method in the field of IT, above all, through David J. Anderson [4] and his book "Kanban: Successful Evolutionary Change for Your Technology Business. " Anderson names the following core practices that characterize the Kanban method:

• Visualizing: The individual jobs in a project and their relationship to the steps of the process are made visible for everyone.
• Limiting work in progress: The pull system, together with a limit on the number of simultaneous tasks, prevents a station (e.g., the QS team in an IT context) from becoming overloaded.
• Managing flow: Informed decisions can be made on the basis of important metrics – for example, the processing time for a certain task, the number of unfinished tasks at a station, or the amount of time a task remains at a particular station.
• Making policies explicit: Agreements are formulated not only for the tasks at each station but for the criteria that must be met for the task to be considered complete and how the transitions between stations are to take place.
• Implementing feedback loops: Daily stand-up meetings on the team and colleague level, as well as cross-team operations reviews, ensure that everyone involved has influence on the continued improvement of the processes.
• Collaborative improvement, evolving experimentally: Scientific models, like the "theory of constraints," for example, and specific experiments help gain insights from which targeted measures for improving the processes can be derived.

Kanban in Practice

The nice thing about the Kanban principle is that only two things are needed to put it into practice: The explicit permission to introduce WIP limits and a board.

The board, whether a whiteboard, bulletin board, or virtual board in the form of a Kanban application, serves to visualize the workflow. On the Kanban board, each process step is represented by a column. Figure 1 shows a very simple example for such a Kanban board. A typical development project could be modeled with columns called "Backlog," "Analysis," "Development," "Test," "Change Preparation," "Production," and "Done." To the other extreme, very large projects might even use multiple, hierarchically staggered boards, whereby one reflects the overall status and others are used to manage individual parts of the project.

Figure 1: On the Kanban board, each process step is represented by its own column. The projects move from left to right.