Well really that is three questions. Firstly what is a kanban?
1. A kanban is a visual signal.
It is a Japanese term meaning a card, brand or sign. In lean production systems it's used as the signal to an upstream part of the process that items are required by a downstream part of the process.
Which leads to the next question. What is a kanban system?
2. A kanban system is a system for managing work that uses (real or virtual) kanbans to control the flow.
Kanban systems were first used in Toyota for manufacturing but are now widely used in a wide variety of applications including health services and knowledge-based work such as software development. In principle a kanban system is a "pull-system" where work is triggered by demand from a downstream part of the process - ultimately by the demand of the consumer or commissioner of the product. The systems use kanban signals to prevent over or under production in various parts of the process. The kanbans may be "real", for example an empty hopper which is sent back on the production line to indicate that more parts of a given type are needed, or "virtual", such as the signals derived from a kanban board when a "story card" is moved out of a column. In both cases they indicate to the upstream process that another item should be produced, processed or selected.
"But hang on! I thought Kanban was a method."
You're right. That's the third question, the third part of what is Kanban. To be crystal clear, we should ask "What is the Kanban Method?"
3. The Kanban Method is an approach to defining and improving kanban systems.
The Kanban Method emerged from work being done by many practitioners in software management, agile and lean methods and new product development during the first decade of this century. The author of the method was David Anderson, but many others contributed or were doing similar work which fed into the method, including Drago Dumitriu, Jim Benson (co-author of Personal Kanban), Don Reinertsen (author of Flow), Karl Scotland, Corey Ladas (author of Scrumban), Alan Shalloway, Arne Rooke, Mattias Skarin... there are many more than I know about. Kanban was first formulated as a method in a paper presented by Anderson at the Agile 2007 conference in Washington DC, and in 2010 Anderson published what is still the principal authoritative text on the method, "Kanban: Successful evolutionary change for your technology business".
As Alistair Cockburn has observed the word "method" may confuse here - he suggests "reflective improvement framework" is closer to the intention (if it weren't such a mouthful I might agree with him!). I would say Kanban is a method, but a method for defining and improving a process, not the process itself or even a process framework. As such people are often confused by what they think are properties of the Kanban Method, whereas in fact they are simply characteristics of a particular kanban system that they have observed. Try not to be confused or you may miss the crucial value that Kanban can bring to your organisation - continuous evolutionary improvement. A method such as Scrumban for example is an application of the Kanban method to a process that starts off as Scrum or Scrum-like. Scrumban is Kanban, but in a particular context!
Elsewhere in this blog I discussed my shortest possible guide to adopting Kanban, based on the underlying paradigm, the principles and the practices of the Kanban Method. Here it is again:
- Change your viewpoint (lean flow paradigm):
See work as flow
- Change your mindset (foundational principles):
Start from here and improve
- Change your process continually (core practices):
Make work and policies visible; make validated improvements