How Expensive is a "Waterfall" Project Plan?
It's impossible to provide trivial quantification of the costs of a waterfall approach. However, there's a lot of places where "up front" engineering adds cost and risk. A waterfall plan adds friction, zero-value administrative costs and (sometimes) extra work.
For software development that doesn't involve "toy" projects, but apply to the magical "real world" projects, it's difficult to justify building the same "real world" thing twice. It's hard to create a detailed and purely economic analysis of this question. Therefore, we have to resort to hand-waving and speculation.
[I put "real world" in quotes, because the "real world" is a kind of dog-whistle phrase that only project managers understand. It appears to mean "projects that fit my preconceived notions" or "projects that can't be done any other way because of political considerations" or "projects constrained by a customer to have a farcical structure". Another variant on this dog-whistle phrase is "the realities of running a business." There's something in their real world that they (a) can't define and (b) prevents any change.]
A few months back, I saw a http://prezi.com presentation that was intended to drive architecture, cost and schedule conversations. The authors were happy. I was left relatively mystified.
There are three relevant issues that don't fit well into a prezi presentation.
- Open Technology questions. If it's new software development, there are unanswered software API, performance, quality, fitness-for-purpose questions. If it's a clone or a clean-room reverse engineering, then there may be few questions. Otherwise, there must be unknowns.
- Open User Story questions. If it's new software development, then the user stories are not complete, consistent and optimized. There must be something missing or extra.
- Open User Experience questions. I'm not a UX person. Tinkering with an Arduino has taught me that even in the most prosaic, simplistic project there is a UX element.
The Standard Gaps
While a presentation can show some elements of UX, it's not interactive. It cannot provide any useful depth on the UX. Failure to do UX exploration (with real interaction) is crazy. Making assumptions about UX is more likely to create cost and risk.
User Stories can be kicked around in a presentation. However. Once the highest-priority user stories are built, and lessons learned about the users, the problem and the emerging solution, then the other user stories can (and should) change based on those lessons learned. Assuming a list of user stories and then committing to a specific schedule enshrines the costs in a bad plan. And we all know that the plan (and the dates) are sacred once written down.
Software does not exist in a vacuum.
I'll repeat that, since it's a hidden assumption behind the waterfall.
Software does not exist in a vacuum.
You have a Heisenberg problem when you start building software and releasing it incrementally. The presence of the new software, even in a first-release, beta-test, barely-working mode changes the ecosystem in which the software exists. Other applications can (and will) be modified to adjust to the new software. Requirements can (and should) change.
A waterfall project plan exists to prevent and stifle change. A long list of tasks and dates exists to assure that people perform those tasks on those dates. This is done irrespective of value created and lessons learned.
Technology changes. Our understanding of the technology changes. One wrong assumption about the technology invalidates the deliverables for a sprint. In a project with multiple people, multiple assumptions and multiple sprints, this effect is cumulative. Every assumption by every person for every technology is subject to (considerable) error.
Every technology assumption must be looked at as a needless cost that's being built into the project.
Recently, I've been working on a project with folks that don't know Django very well. Their assumptions are -- sometimes -- alarming. Part way through a sprint, I got a raft of technical questions on encrypting passwords. It's hard to state it strongly enough: never encrypt a password. What's more useful is this: always hash passwords. The original password must be unrecoverable. There are lots of clever hashing techniques. Some of which are already part of Django. A significant portion of the sprint (appeared) to be based on reinventing a feature already part of Django.
Do the math: a few wrong assumptions made during project planning are canonized forever as requirements in the project. With a waterfall project, they're not easy to change. Project managers are punished for changing the project. You can't increase the project deadline; that's death. You can't decrease it, either: you get blamed for sand-bagging the estimates.
Arduino Technology Lessons Learned
After buying several 74HC595 shift registers from Sparkfun, I realized that my assumptions about the interfaces were utterly wrong. I needed to solder a mix of right-angle header and straight-through headers onto the breakout boards. I tried twice to order the right mix headers. It seems so simple. But assumptions about the technology are often wrong.
This is yet more anecdotal evidence that all assumptions must be treated as simple lies. Some managers like to treat assumptions as "possibly true" statements; i.e., these are statements that are unlikely to be false. This is wrong. Assumptions always have a very high probability of being false, since they're not based on factual knowledge.
Some managers like to treat assumptions as "boundary conditions": i.e., if the assumption is true, then the project will go according to plan. Since all of the assumptions will be prove to be incorrect, this seems like simple psychosis.
[Interestingly, the assumptions-are-boundary folks like to play the "real world" card: "In the real world, we need to make assumptions and go forward." Since all assumptions will be shown to be incorrect, why make them? Wouldn't it be more rational to say "we need to explore carefully by addressing high-righ unknowns first"? Wouldn't it be better to both gather facts and build an early release of the software at the same time?]
Arduino User Story Assumptions
After building a prototype that addressed two of the user stories, it slowly became clear that the third user story didn't actually exist.
Sure, the words were there on paper. Therefore, there's a user story.
There was nothing to actually do.
The whole "As a [role], I need [feature] so that I can [benefit]" that was written on day one was based on a failure to understand precisely how much information was trivially available. The benefit statement was available with a small software change and no separate user story. And no separate hardware to support that user story.
Exploration and tinkering reduced the scope of the work. In the real world.
[In the "real world" where waterfall is considered important, exploration is described as unbounded spending of limited resources. In the real real world, money must be spent; it can either be long hand-wringing meetings or it can be prototype development.]
The user story (written before a prototype existed) was based on a failure to fully understand the UX. The only way to fully understand the UX is to build it. Education costs money.
Arduino UX Learnings
Perhaps the most important issue here is UX.
Once upon a time, UX was expensive, difficult and complex. So difficult that special-purpose prototyping tools were created to make it possible to create a preliminary UX that could be used to confirm UX and user stories.
This UX prototyping effort was real money spent as part of "requirements" or "design"; it created documentation that flowed over the waterfall for subsequent development.
This notion is obsolete. And has been obsolete for several years.
UX is now so easy to build that it makes much more sense to build two (or three) competing UX's and compare them to see which is actually better.
Indeed, it makes a lot of sense to build one UX and release it; make a real effort at solving the user's problems. Then build a second UX for A/B testing purposes to see if there's room for improvement.
I'll repeat that for folks who really like the waterfall.
It's now cheaper to actually build two than it is to write detailed requirements for one.
[In the "real world", this is deprecated as "wasting time playing with the UX". As if written requirements based on nothing more than a whiteboard are more "real" than hands-on experience with the UX.]
You can prove this to yourself by actually observing actual UX developers knocking out pages and screens. Long "requirements gathering" meetings with prospective users amount to a waste of time and money. Long "brainstorming" sessions, similarly, are wasteful. Short, ongoing conversations, a build, a release, and a follow-up review has more value, and costs less.
Do the math. Several users and business analysts in several multiple-hour meetings costs how much?
A pair of developers banging out fully-functioning, working UX for a use case costs how much?
A slavish adherence to waterfall development creates "real world" costs.
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