The Old Joel on Software Forum: Part 4 (of 5)

Lean == critical chain ?

Dumb question: I frequently read about the "lean"/"agile" development style on the one hand, and "critical chain" or "theory of constraints" management on the other.

Are these two concepts related in any way, or completely different?

My impression is that "critical chain" starts at conventional project management and adds some flexibility, whereas "agile" is (or claims to be) a radically new approach - but I could be totally wrong on this?

- Roland
Monday, March 8, 2004

There is some overlap in the strategies and tactics used in both approaches, but there are also some differences.

For example, lean derives from manufacturing discipline that considers work in process (WIP) to be muda, or waste, no matter where it occurs in the system.

Critical chain, being a derivative of theory of constraints (TOC) thinking, generally looks at WIP as being of two different types: waste or protection. TOC solutions invariably seek to protect the constraint from systemic variation by locating an amount of WIP before the constraint. Excess capacity has a similar distinction in the two approaches.

The two disciplines also share a lot of overlap (even if they come to their conclusions from different directions). For instance, both approaches carefully control the introduction of new work into the system based on the capacity of the entire system to absorb it. TOC/CC controls this using a "rope" signal based on the status of the constraint resource, and lean approaches use variations of the kanban approach.

Agile shares some properties with both of these, but in my mind it is distinct, and tailored to a system that must support low volume and a lot of variation in its products.

chirp
Monday, March 8, 2004

Heya Roland,

Sorry, I can't answer your questions directly, but maybe you'd be interested in these articles:

http://www.poppendieck.com/time.htm
http://www.poppendieck.com/papers/Logistics.PDF

Their book is a good read, though I don't have enough management experience to judge it.

VP
Monday, March 8, 2004

Thanks VP, I recently read Poppendieck's Lean SW Development. I liked it too, but it was a bit too, uhm, general for my taste. In fact, I posted the question to in order to decide whether my next book will be Leachs "Critical Chain Project Management" or some Agile book (Cockburn? Highsmith?).

- Roland
Monday, March 8, 2004

Larry Leach is working on a new version of his book. I'm not sure when it's projected to be completed. It may be useful to you to read the alternatives while waiting for the next edition of the book, though.

chirp
Monday, March 8, 2004

How about "Critical Chain" By Goldratt?

That was pretty good.

Or the "XP Explained" / "XP Installed" series. I really liked those ....

Matt H.
Monday, March 8, 2004

Roland,

Yeah their book is quite general, on purpose I would imagine. Not a good book for giving you a starting point.

I'd be interested to hear what book you decide on and what you think of it.

VP
Tuesday, March 9, 2004

>some Agile book (Cockburn? Highsmith?).

Check out Alistair Cockburn's web site. There's a lot of material there.

John Rusk
Thursday, March 11, 2004