Decrease Friction, improve flow, get better feedback.

Brad Appeltion summarizes The Theory of Constraints (ToC), Lean manufacturing, and Agile software development with three words Friction, Flow, and Feedback.

He says:

  • ToC is about removing friction,
  • lean is about improving flow,
  • and Agile is about getting better feedback sooner.

But all of these things actually describe Lean. The briliance of the Toyota Production System is that it tells you how to removE friction through the reduction of waste (motion, long cycle times, poor quality, etc), creating a clear flow of work through your system, and reducing the time between a customer asking for something and when it is delivered. And that helps to make the Feedback loop is as short as possible.

7 Responses to “Decrease Friction, improve flow, get better feedback.”


  1. All very true. This is why cash flow based accounting systems promote lean manufacturing, and why Toyota has always maintained cash flow and market share as thir most important metrics.

    American manufacturers struggle with lean because of their blind adherence to the Sloan/DuPont Roi management and accounting systems.

    “reducing the time between a customer asking for something and when it is delivered” doesn’t make sense in the Sloan system, in which inventory is classified as an asset, and P&L performance can be artificially improved by calling ‘time out’ along this time line whenever you want.

  2. Agreed Cash Flow Accounting is simpler and more direct. Lean counts unsold inventory as a liability (it takes cash to store and maintain) while accrual systems count it as an asset.

    But as I see it if you can’t sell it it’s not an asset. And if you could sell it, you wouldn’t be calling it unsold inventory, would you?

    Even though this is an oversimplification, I think it helps drive home the point that people have begun to think very strange things about what counts as an asset on the balance sheet.

  3. I agree that all of these things apply to Lean. They all also apply to agile development too. I think the distinction is what the primary focus or emphasis is upon in each of these approaches. Feedback certainly applies to “Lean”, but Lean doesnt centrally emphasize feedback — Agile development centrally emphasizes feedback (and adapting in response to it). In Lean, thats simply a particular tool/technique to apply toward maximizing flow and minimizing waste (which is what Lean seems to centrally emphasize). TOC focuses on identifying and removing “the constraint” of a system (whatever system it may be).

  4. I agree with you that feedback is the primary message of Agile, and I think that it is critical to project success.

    But, when you say “Lean doesn’t centrally emphasize feedback,” I think you are missing an important part of the lean message.

    Perhaps feedback isn’t the core of what lean people _talk_about_, but it is central to two of the most important “lean tools:” the pull system and one-piece-flow are designed around removing long feedback cycles.

    Defects need to be detected as soon as possible after they are created, and one-piece-flow makes that much more likely. Products which immediately go to customers with no waiting mean customer feedback comes sooner.

    The Lean/Feedback connection is even more central to the product design side of Toyota which treats any activity which does not result in organizational learning as waste.

  5. Hi Mark! I’m not missing the “Lean” message (honest), Im commenting on how the Lean literature communicates that message. And I’m asserting that it emphasizes feedback substantially less directly (almost indirectly) and emphasizes flow very directly. When it does touch on feedback, it always appears to be a byproduct of focusing on flow.

    I dare say that “pull systems” and “one piece flow” are both examples of this. I’m not saying it doesnt discuss the feedback, Im saying is does so as a result of focusing on flow (rather than the other way or around, and rather than emphasizing both equally – it still seems to me that “flow” is the prime directive, and pull-systems and one-piece-flow are in service to that.

    Agile on the other hand quite possibly emphasizes “reducing the cost of change” more than feedback (maybe), but much more directly emphasizes feedback loops at all levels of scale in order to benefit from early detection+correction.

    You mention “importance” a couple of times – I dont see this as being about importance, but about emphasis and focus of communication about the methods (Agile, Lean & TOC).

  6. Brad,

    That makes sense.

    I agree that the focus of Lean is on flow, and that quicker feedback is a byproduct of that. By in large I think this tactic is successful because one piece flow makes feedback “automatic” by assuring that quality problems are detected as soon as possible.

    I also agree that XP’s is driven by feedback via: the “on-site-customer”, short iterations, unit tests, continuous integration, etc. All of these practices are based on the principle of getting better feedback sooner, and together they form a much more comprehensive set of feedback mechanisms than anything you will find in Lean. Which is only to be expected because Lean Manufacturing usually doesn’t need as much feedback as software development. There’s just not as much risk of doing it wrong when you are building the same (or mostly the same) thing over and over again, as there is when each thing you build is entirely new.

  7. Mark,

    Agreed! The development of the software itself is inherently more focused on acquiring, creating and codifying knowledge than “production” activities are. That touches on one of the other reasons why feedback is emphasized in agile methods: for collaboration and emergent behavior of self-organizing teams.

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