This is one of those pictures tossed out at some conference that drives me crazy. It's uninformed, ignores the disciplines of developing software for money, and is meant to show how smart someone is, without actually understanding the core processes needed for actually being knowledgeable of the topic - in this case statistical processes of project work. Then the picture gets circulated, re-posted, and becomes the basis of all kinds of other misunderstanding, just like the Dilbert cartons that represent cartons of the problem, but have no corrective actions associated.
It is popular in some circles of agile development to construct charts showing the strawman of deterministic and waterfall approaches, then compare them to the stochastic approaches and point out how much better the latter is than the former. Here's an example.
These strawman approaches are of course not only misinformed, they're essentially nonsense in any domain where credible project management is established, and the basis of the their response with Don't Do Stupid Things on Purpose.
Let's look at each strawman statement for the Deterministic View in light of actual project management processes, either simply best practice or mandated practice.
- Technologies are stable - no one believes this that has been around in the last 50 years. And if they do, they've been under a rock. Suggesting this is the case ignores even the simplest observations of technology and it's path of progress.
- Technologies are predictable - anyone who has any experience in any engineering disciplne knows this is not the case. Beyond the simplest single machine unintended consequence and emergent behavior with obvious.
- Requirements are stable - no they're not. Not even in the bone head simplest project. This would require precognition and clairvoyance.
- Requirements are predictable - no they're not. Read any Requirements Management guidance, any requirements elicitation process, or work any non-trivial project to learn this as a cub developer.
- Useful information is available at the start - this would require clairvoyance.
- Decisions are front loaded - this ignores completely the principles of microeconomics of decision making in the presence of uncertainty. Good way to set fire to your money. For a good survey of when and how to make front loaded decisions see Making Essential Choices with Scant Information. Also buy Williams other book Modelling Complex Projects. Along with another book Project Governance: Getting Investments Right. This statement is a prime example of not doing your homework before deciding to post something in public.
- Task durations are predictable - all task duration are driven by aleatory uncertainty. For this to be true, the laws of stochastic process would have to be suspended. Another example of been asleep in the High School statistics class.
- Task arrival times are predictable - same as above. Must have be a classics major in college. With full apologies to our daughter who was a classics major.
- Our work path is linear, unidirectional - this would require the problem to be so simple it can be modeled as a step by step assembly of Lego parts. Unlikely in any actual non-trivial project. When system of systems becomes the problem - any enterprise IT project, any complex product - the conditions of linear and unidirectional go out the window.
- Variability is always harmful - this violates the basis of all engineering systems, where Deming variability is built into the system. Didn't anyone who made this chart read Deming?
- The math we need is arithmetic - complete ignorance of the basic processes of all systems - they are statistical generating functions creating probabilistic outcomes.
The only explanation here is the intentional ignorance of basic science, math, engineering, and computer science.
In the stochastic View there are equally egregious errors.
- Technologies are evolving - of course they are. Look at any technology to see rapid and many times disruptive evolution. Project management is Risk Management. Risks are created by uncertainty - reducible and irreducible. Managing in the presence of uncertainty is how adults manage projects.
- Technologies are unpredictable - in some sense, but we're building systems from parts in the market place. If you're a researcher at Apple this likely the case. If you're integrating an ERP system, you'd better understand the process, technology, and outcomes, or you're gonna fail. Don't let people who believe this to spend your money.
- Requirements are evolving - of course they are. But the needed capabilities had better be stable or you've signed up for a Death March project, with no definition of done. But requirements aren't the starting point, Capabilities are. Capabilities Based Planning is how enterprise and complex projects are managed.
- Requirements are degree of freedom - have no idea what this means. Trade Space is part of all good engineering process. Wonder if the author or those referencing this chart know that.
- Useful information is continuously arriving - of course it is. This work is called engineering and development. Both are verbs.
- Decisions are continuous - of course they are. This is the core principle of microeconomics of all business decision making. But front-end decisions are mandatory. See "Issues on Front-end decision making for some background before believing this statement is credible. And a summary of the concept of the Williams book above.
- Task arrival times are unpredictable - this is intentional ignorance of stochastic processes. Prediction always includes confidence and a probability distribution. Predictions is simply saying something about the future. For task arrival time to be unpredictable, those time would have to be completly chaotic, with no underlying process to produce them. This would be unheard of in project work. And if so the project would be chaotic and destination to fail starting on day way. Another example of asleep in the stats class.
- Our work path is networked and recursive - of course it is. But this statement is counter to the INVEST condition of agile which is present in only the simplest project.
- Variability is required - all processes are stochastic processes. A tautology. Natural variability is irreducible. Event based variability is disruptive to productivity, quality, cost and schedule performance and the forecasting of when, how much, and what will be delivered in terms of Capabilities. Uncontrolled Variability is counter proper stewardship of your customer's money.
- The math we need is probability and statistics - yes, and you'd better have been paying attention in the High School statistics class and stop using terms you can't refer to in the books on your office shelf.
In the End
For some reason using charts like this one, re-posting of Dilbert cartons, making statements using buzz words - we're using Real Options and Bayesian Statistics to manage our work - are may favorite ones - seems to be more common the closer we get to the sole contributor point of view. Along with look at my 22 samples of self-selected data with a ±70% variance as how to forecast future performance.
It may be because sole contributors are becoming more prevalent. Sole contributors have certainly changed the world of software development in wasy never possible by larger organizations. But without the foundation of good math, good systems engineering - and I don't mean "data center systems engineering," I mean INCOSE Systems Engineering - those sole contributor points of view simply don't scale.
Always ask when you hear a piece of advice - in what domain have you applied this advice with success?