Tuesday, January 17, 2006

The Unchangeable Rules of Software Change

I dont think I've ever written this down before, but I commonly say this to many a developer and development team. I often come across teams in the early stages of learning to deal with changing requirements. They typically run into two pitfalls in the following order:
Pitfall #1: No scope change-management
The very first pitfall they fall into is not having any kind of change-management for the project/requirements. They allow any and all changes in a very reactive fashion without thinking about trying to renegotiate the scope, schedule, or resources for the project/release.

Pitfall #2: Preventing scope changes
The very next time around, they run into the second pitfall: they overcompensate for being burned/bitten by the first pitfall by trying to prevent any and all changes to the scope of their next product release.
They keep insisting that the fundamental problem is they dont have completely stable detailed requirements. If the requirements were detailed enough up-front, they think their estimates would be more accurate; and if only the requirements would stop changing before a single line of code is written, then the schedule wouldn't keep fluctuating so much. It's those darn users/customers/analysts that don't know what exactly they want at the outset. It's all their fault!

The irony is that the more they try to get stable detailed requirements up-front, the more the schedule becomes protracted: first to get all the gory-details analyzed and specified up-front; and second because so many of the gory-details were either incorrect or still not detailed enough. It becomes this vicious cycle of trying to prevent change with more up-front detail, and yet things keep getting worse instead of better.

The first thing I commonly do here is explain the following:
    There is a very fancy technical term that biologists use to describe completely stable systems. This highly sophisticated technical term is the word "DEAD!"
I then try to explain that we meager humans (including ourselves and our customers) are imperfect, and we have imperfect and incomplete knowledge: We don't know things, and we don't know that we don't know things, and we don't know how to find out many of those things earlier.

Then I tend to mention Phil Armour's description of the Five Orders of Ignorance and how Software is not a Product, and that software development is a therefore a knowledge creation activity which involves reducing our ignorance over time though learning and discovery about the domain (our requirements) and ourselves (our process, culture, and skill/capabilities).

At this point I then introduce them to my "tried and true, battle-proven and industry-acknowledged, Unchangeable Rules of Software Change":
Rule #0: Change is Inevitable!
The Requirements/Plans ARE going to change!

Rule #1: Resistance is Futile!
There isn’t a darn thing you can do to prevent Rule #0.

Rule #2: Change is like Quicksand -- Fighting it only makes it worse!
The more you try to deny and defy rule #1 by attempting to prevent rule #0, the worse things will get.

Rule #3: Change is like Quicksilver -- Tightening your grip makes it slip from your grasp!
The more you try to deny and defy rule #2 by attempting to precisely predict, or rigidly control change, the more erratic and onerous the result will be.

Rule #4: Embrace change to control change
The more flexible and adaptive you are at accommodating change, the more control you will have over it.
Recently I was talking to a group that was struggling with rule #2. They thought if they could only do even more detailed specification up-front (they already do a reasonable amount of up-front detail), that it would somehow eliminate problems with estimation accuracy, which in turn would alleviate problems with "conformance to plan" and prevent the details from being discovered later (because they would instead get them all "right" up-front).

Despite having plenty of historical evidence/data in this particular product to support the "inescapable truth" laid out by these rules, there still seemed to be that desire to cling to the illusion of control that we can somehow prevent such changes if only we spend more time+effort getting a more complete+perfect+detailed spec up-front.

I was searching for external validation ("not invented here") and then came across the following three things that I liked a lot:


Unknown said...

Changing requirements or plans is a side effect. The root effect is that people constantly change their mind because they live and learn constantly.

There is one way to stop that: death. And that's what happens to a project that does not allow requirements to change.

What you can do is reduce the amount of changes by shortening the project.

An infinitely short project will have infinitely little creep (and probably infinitely little results too).

Brad Appleton said...

Thanks Frank! That remains me of another "little ditty" I commonly say when I encounter this situation: I talk about how a completely stable project (or requirements) is like a completely stable system, and that biologists describe such completely stable systems as "dead!"

I just added mention of this in the blog-entry, as well as mentioning to the two pitfalls I typically see that lead up to me giving this "speech."