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There are unknown unknown in projects, people won't pay you for a full analysis and there is always the option that one library you rely on has a nasty bug you

There are unknown unknown in projects, people won't pay you for a full analysis and there is always the option that one library you rely on has a nasty bug you cannot foresee. One doesn't have to go very far and look for psychological issues when a major source of indeterminism comes from directly the imperfect tooling itself we use. Sometimes software is compared to construction, except you don't get to start with a perfectly detailed environment to build your software on. Until we have this major source of indeterminism in the tools themselves, pretending to fix issues on the estimation process alone is a fool errand. I believe a as-400 project can be estimated fairly well now based on previous experiences. But how would you go estimating a project relying on, say, local browser storage? The only way is to go and build it and identify all the pitfalls yourself, and then the browser landscape changes and you get set back all over again. Just following Safari rules on IOS to obtain a full screen mode sets us back a week on almost every releases. We started before they started messing with stuff, now we include a week of fixes in the schedule for every major IOS update, but we had no chance to predict this when the project started.

jacques_chester 11y ago
Building construction is actually a good analogy. For stuff that's been built a thousand times, you can state with a fair amount of confidence how long a project should take and how much it should cost. You can obtain financing and insurance because the dataset is large enough. For stuff that's unusual or bespoke -- the kind of thing that will appear in an architecture magazine or in a newspaper investigatory report -- then estimates are very likely to be wildly optimistic. So it's the same, insofar as the further you stray into research, the less certainty there is. The bigger the bet, the fewer such things have been built, the bigger the risk will be that things go awry. I have a book in my collection -- Industrial Megaprojects -- which makes fascinating reading for enumerating all the ways that chemical process plants, giant mines, gas pipelines, gigantic factories etc can blast through the budgets and schedules. My personal favourite: a chemical plant built relying on an adjacent river for cooling. To save costs, only one water temperature sample was taken during planning ... in winter. Three billion dollars later, the owners found that the plant was inoperable for about half the year because the river water was too warm.
- RyJones 11y ago
  I worked building a bank once where a detail cost us a bunch of heartburn estimating and building. Having the architect stop by, look at it, and say "I had no idea if you guys could build that" was infuriating.

jacques_chester 11y ago

Building construction is actually a good analogy. For stuff that's been built a thousand times, you can state with a fair amount of confidence how long a project should take and how much it should cost. You can obtain financing and insurance because the dataset is large enough. For stuff that's unusual or bespoke -- the kind of thing that will appear in an architecture magazine or in a newspaper investigatory report -- then estimates are very likely to be wildly optimistic. So it's the same, insofar as the further you stray into research, the less certainty there is. The bigger the bet, the fewer such things have been built, the bigger the risk will be that things go awry. I have a book in my collection -- Industrial Megaprojects -- which makes fascinating reading for enumerating all the ways that chemical process plants, giant mines, gas pipelines, gigantic factories etc can blast through the budgets and schedules. My personal favourite: a chemical plant built relying on an adjacent river for cooling. To save costs, only one water temperature sample was taken during planning ... in winter. Three billion dollars later, the owners found that the plant was inoperable for about half the year because the river water was too warm.

RyJones 11y ago
I worked building a bank once where a detail cost us a bunch of heartburn estimating and building. Having the architect stop by, look at it, and say "I had no idea if you guys could build that" was infuriating.