[bumby]

Something often overlooked in cost/schedule estimates is the nature of joint probability of actions slipping. Action A slips and causes action B to slip. I think software is tougher to estimate because the number of interfaces is often much higher, and sometimes more hidden, than in hardware.

[bdangubic]

as opposed to say building a house where framing can totally slip while we run electricity and build a roof floating in mid-air

software is only tougher to estimate if incompetent people (vast majority of the industry, like 4+ million) is doing the estimating :)

[yetihehe]

My home construction slipped 6 months on 2 year build time. It happens in construction very often.

> software is only tougher to estimate if incompetent people (vast majority of the industry, like 4+ million) is doing the estimating :)

No, it is tough to estimate, but not only for incompetent people. And "incompetent" can be stretched to "don't know what he's doing", which is how I operate most of the time. I don't know what really needs to be done until it's done. Main part of my work is research on what actually needs to be done, then "just" implementing it. If I waited with estimating until I know what needs to be done, I would spend 3/4 time estimating and then 1/4 with clear understanding and good schedules (example description: I will be clicking keys for 5 hours).

[rkomorn]

> My home construction slipped 6 months on 2 year build time. It happens in construction very often.

Tangent, but I have at least 3 friends that would've (in retrospect) been nothing short of ecstatic if their home construction had "only" slipped 6 months on a 2 year timeline.

[bumby]

That’s a bit of a strawman considering I was deliberate in saying hardware interfaces are limited and not saying they are zero. The number of interfaces in software is often going to be orders of magnitude greater. The network effects and failure modes will often increase geometrically with the number of interfaces. In fact, big construction design firms have tools to easily identify and mitigate the “clashes” you bring up and those tools tend to work well because there is a finite number and the designs are well-documented (as opposed to software where changes are relatively cheap and easy so they often occur without documentation)

Saying incompetence is the reason is a trivial rebuttal that ignores the central claim about complexity. It’s like saying “the reason why we don’t have a theory of everything is because we don’t have competent physicists”