Wednesday, April 11, 2007

Lean Software Development - 1

Mary & Tom Poppendieck will be visiting Charlotte to give their Lean Software Development - Practitioner's course on May 9-10. [Written in 2007]

Partly because of that and because of an inquiry, I wanted to talk some about Lean. Specifically, about waste, which is known as muda in Japanese.

Earlier I posted about waste. This is a different perspective on the same basic subject.
Those who know Lean manufacturing know that Shigeo Shingo defined the Seven Wastes for manufacturing (derived from his work at Toyota).  (Well, some say Taiichi Ohno identified the 7 wastes. Oh well.)  The Poppendiecks have defined the Seven Wastes of software development. See below.


Software Development

In-Process Inventory
Partially Done Work
Extra Features
Extra Processing
Task Switching

Some of them are obvious. Some maybe not.

Let’s pick on the first row. What is Partially Done Work?

The Poppendiecks identify several examples:
  • Uncoded documentation
  • Unsynchronized code
  • Untested code
  • Undocumented code (if documentation will be needed; usually some will be needed in my experience)
  • Undeployed code
In fact, any work done prior to receiving the business benefits of the deployed software is “partially done work”.

Why is this waste? After all, from an accounting point of view, this is “inventory”, which is an asset. Right? (And so thought the auto industry for the longest time.)

But, what good can happen with or to partially done work? (My answer: almost nothing.)

And what bad can happen to partially done work? Lots. Every minute it is undeployed is a minute the customer is left unsatisfied. And with time, la donna e mobile (see lyrics), and so the customer’s needs also change. Ever happen to you? I would bet it has.

We lose our knowledge and understanding of that unfinished work. (What's the half-life of our memory of a Requirements Doc, when we have worked on two more in the meantime?) People lose it, it gets harmed. We have to do Task Switching to come back to it.

Further, thousands of dollars have been invested in that unfinished work, which often can’t even be shown to the customer. The firm has to fund that investment, and the customer loses confidence that the development team can produce anything worthwhile. And the development team is unsure…how near finished is it, really? You have a guess, but nothing beats getting the ball over the goal line (oops, football metaphor, wrong season).

“But, but, but”, you complain, “I must have some partially done work.” Yes, indeed the team must. So, the goal is to limit that waste to the smallest amount possible. Example that might fit your situation: Only one story in-flight at a time.

More on waste later.