> There's a huge, huge difference between doing relative point-based estimation and date-driven, pointy-haired-boss estimation, and it's a total disservice to the software community that so many engineers seem to not really understand that difference, and seem to think that the only two options are "unrealistic date-based estimates" and "no estimates."
This was my beef with the article too. Basically on the one hand he proposes a strawman composed of known-worst practices (estimate-by-deadline, estimate-by-gut, ad hoc estimation and so on) and thereby tars all estimation with the brush ... except for the one alternative he approves.
This is the fallacy of dichotomy.
The root problem is the concept that estimates have to be accurate. Well, duh, they can't be. The bigger the project, the more people, the longer the timeframe, the less likely the project is to meet the estimate.
That's why you don't perform one estimate.
That's why you have confidence bands on estimates.
The whole blog article feels like a pastiche of criticism cribbed from agile books and not from a direct, thoughtful engagement with the primary or secondary literature on software project estimation.
I'm only 31. By any measure I'm still a young man. Why do I feel like such a curmudgeon all the time? Because apparently nobody reads books or papers any more. It's all blogs citing blogs who echoed the summary of the notes of the review of a single book.
One more thing. There's a difference between a plan and an estimate. Plan-and-control is not the same thing as performing an estimate; DeMarco's self-criticism is not directly applicable.
This is why I agree with the original article over these comment parents. I work in a small software agency for clients who would never grasp the Cone of Uncertainty. They are much closer to the pointy-haired boss type than the type of person who appreciates the finer points of software project estimation. While reading the literature is good, the average developer will seldom find the time to do so. And even if they do, an off-the-cuff estimate is often better than carefully planned specification documents that no business stakeholders will ever read.
Of course accurate estimates have tremendous business value. But in reality they often come at the expense of what the client really needs which is delivery of features. I have seen estimation and tight project control taking up substantially more time than delivering actual features. And it was exactly as the OP stated:
> Software projects that require tight cost control are the ones delivering little or no marginal value.
The lesser the project value the tighter the control leading to a vicious cycle of developers cutting corners and increased micro-management.
Clients sometimes want an estimate of how long a single feature or fix will take, even when it will take only 15 minutes. The communication overhead and time spent estimating easily outweigh the time to implement.
It's unfortunate that so much of the literature on relative estimation/story points/velocity/planning poker ends up intertwined in agile-development-consultantese, so sometimes reading some of these things, you have to take it with a serious grain of salt and weed out all the BS and dogma to get to the useful and important bits. The important bits there are really pretty simple:
* Estimate in terms of points, not days, and estimate tasks relative to one another
* Use planning poker (or something like it) within the team to get more accurate estimates
* Empirically measure how many points you do in a given period of time to come up with your "velocity". To do that, you have to be pretty honest about things being "done done" before you move on to the next task; otherwise it's too easy to fudge and your numbers are worthless. "Oh, yeah, we did 10 points of work, well, except for writing the tests or doing the styling . . ."
Remember that velocity is NOT a productivity measure, it'll change over time, and it'll change if the team members change or if other external factors intervene, like an increase in support requests or something. So this technique kind of only works if your organization isn't already dysfunctional: as soon as velocity is seen as a productivity measurement, you're pretty screwed.
That's pretty much it. The relative estimates let you prioritize work appropriately (i.e. "I'd rather have these five 1-point stories than this one 5-point story, so we'll do those first"), and the velocity lets you track how fast you're actually going and about when you'll be done with a given chunk of work, so you can adjust plans as needed.
Note that relative estimation doesn't work nearly so well for large-scale estimation, or for greenfield development where you don't know what you're doing yet. For large-scale planning, my company will generally just give a SWAG in terms of points (we think this feature is 100 points) to give us at least some initial idea of expected relative sizes of things, then we'll compare that initial SWAG to the actual points as we break things out into more bite-sized stories that we can estimate more accurately. If we feel like we're half way through the feature and we've already done 70 points of work, that's a signal that we need to up our estimate for the remainder of the work. Steve McConnell's book is good as well, though honestly we don't really do much in the way of confidence-based estimates at this point. My experience is that out of every 10 projects we do, 8 or 9 will be within 20% of our initial SWAG and 1 or 2 will blow out to 2 or 3x the initial estimate. Of course, we never know which ones will blow out, we just know something will. In other words, we don't bother with confidence intervals at the individual feature level, we just do it at the macro level. So if a team has a velocity of 10 and we have 26 weeks to deliver a release, giving us a hypothetical total capacity of 260 points, we'll "commit" to maybe 2/3 of that. So we say "Okay, this first 170 points we're pretty sure we can get done. Anything after that will be a bonus."
I thought Cohn's book was good, but a bit padded out.
Basically all that agile really changed is how often folks take a sounding. Velocity is basically a productivity metric, it's a first derivative of project size (hence ... velocity).
But I mean you could always do that with traditional estimates.
That's pretty much what an Earned Value chart does.
Don't get me wrong: agile is an improvement. But it is an improvement that is evolved from what came before; not a categorical change. Looking at the historical literature still pays dividends to thoughtful engineers.
This was my beef with the article too. Basically on the one hand he proposes a strawman composed of known-worst practices (estimate-by-deadline, estimate-by-gut, ad hoc estimation and so on) and thereby tars all estimation with the brush ... except for the one alternative he approves.
This is the fallacy of dichotomy.
The root problem is the concept that estimates have to be accurate. Well, duh, they can't be. The bigger the project, the more people, the longer the timeframe, the less likely the project is to meet the estimate.
That's why you don't perform one estimate.
That's why you have confidence bands on estimates.
The whole blog article feels like a pastiche of criticism cribbed from agile books and not from a direct, thoughtful engagement with the primary or secondary literature on software project estimation.
I'm only 31. By any measure I'm still a young man. Why do I feel like such a curmudgeon all the time? Because apparently nobody reads books or papers any more. It's all blogs citing blogs who echoed the summary of the notes of the review of a single book.
One more thing. There's a difference between a plan and an estimate. Plan-and-control is not the same thing as performing an estimate; DeMarco's self-criticism is not directly applicable.