Software engineering's preoccupation is the arrangement of
bits,
as opposed to
atoms.
One of the properties of bit arrangements is that their marginal
manufacturing cost is zero; once you have an arrangement of bits, you
can make as many exact copies of that arrangement as necessary,
whenever and wherever they're needed. By contrast, an arrangement of
atoms such as a bridge has a large marginal manufacturing cost, even if
you just want an exact copy. Further, there are few physical limits to
bits, while there are sharp physical limits to atoms. The only real
limit to bit arrangement is the human brain, and economics (how badly
people want bits arranged in particular ways).
These are the fundamental reasons why
nearly every software engineering project is attempting new design, and is thus hard.
This is because, in the world of software, design equals bit
arrangements and copying a prior bit arrangement has zero cost.
Finding an appropriate bit arrangement used to have substantial cost,
but that cost is falling towards zero too. So for a given project, you
can assume that competent software engineers have mostly found and
copied the relevant patterns of bits where possible, and the remaining
work is
design.
Think about what the statement above means. This isn't like a civil
engineer dealing with slightly differing terrain or traffic loads when
adapting an existing design for a new bridge; it's more like a civil
engineer being asked to build a bridge out of Jello on Pluto. And the
next time, to build atop a moving lava flow on Mercury. In other
words, with the easy, mechanical adaptations being taken care of by
those ubiquitous bit patterns, the problems that are left for people to
work out are the hard, surprising, novel ones. Usually with nonlinear
And in software, design really is everything; once you've taken design
to a detailed enough level that the implementation is mechanical... we
let the machines do it.
Which is why I winced when I read
Scott Rosenberg's interview in Salon.
He gets it exactly right when he notes that there's always something
new in every software project, otherwise there'd be no point in doing
it. But he goes off the rails when he says, "...programmers are
programmers because they like to code -- given a choice
between learning someone else's code and just sitting down and writing
their own, they will always do the latter." Jonathan Rentzsch has
already
skewered
this statement better than I could. It is of course true that there
are some people who just aren't good at finding prior solutions, or at
understanding them once found, and they may contribute to unnecessary
re-creation of software, increasing both cost and risk to larger
projects. But they're not the norm, and aren't a major cause of the
"always something new" phenomenon. The essence of software development
is new design.
This is also why attempts to map manufacturing based activities to
software development are at best rough approximations and at worst
dangerous distractions. Software development is a knowledge
acquisition activity, not a manufacturing activity.
