I was talking with my friend Clarke Ching today about Kanban and pull systems in general. I came up with a metaphor that we both liked and thought I would share it.
Problem : Imagine you want to get a ball of string ( your features ) through to the other side of a funnel ( your development team ).
Traditional methods involved pushing REALLY, REALLY HARD until it goes through.
Agile and other iterative methods realise that trying to force a whole ball of string through a funnel at once is madness, so they chop the string up into smaller pieces which are easier to push through.
Pull systems, such as Kanban, change the dynamic, rather than pushing the string through, they feed the tip of the string through and then pull it as fast as they can.
Which of these is best?
Well, traditional methods often cheat by mashing some subset of the string through and declaring victory. Or by making the team ( the funnel ) enormous so that you can fit a fairly large ball of string through the hole without effort. Or by minimising the features so that they’re dealing with a tiny ball of string. Or some combination of the above. I’m not sure this is ever a good idea.
Agile works pretty well, but the chopping takes effort ( iteration planning ) and consumes time. But it does break down into nice, neat iterations which provide clear points for releases, milestones, measurement and feedback.
Kanban works pretty well too, it might be slightly more efficient than an iterative Agile approach, but the milestone and release points need to be superimposed onto it since there are no natural break points.
Lean and ToC have their place here too - tools, techniques and strategies to make the hole in the funnel wider and to make sure that the string that gets through is the right string, used as efficiently as possible. Stretching the funnel as far as possible, just as I have stretched this metaphor.
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