  Are there qualitative and quantitative traits of system design that
contribute to the ability of people to further innovate? We propose that
extrinsic adaptability, the ability given to secondary parties to change a
system to match new requirements not envisioned by the primary provider, is
such a trait. "Extrinsic adaptation" encompasses the popular concepts of
"workaround", "fast prototype extension" or "hack", and extrinsic adaptability
is thus a measure of how friendly a system is to tinkering by curious minds. In
this report, we give "hackability" or "hacker-friendliness" scientific
credentials by formulating and studying a generalization of the concept. During
this exercise, we find that system changes by secondary parties fall on a
subjective gradient of acceptability, with extrinsic adaptations on one side
which confidently preserve existing system features, and invasive modifications
on the other side which are perceived to be disruptive to existing system
features. Where a change is positioned on this gradient is dependent on how an
external observer perceives component boundaries within the changed system. We
also find that the existence of objective cost functions can alleviate but not
fully eliminate this subjectiveness. The study also enables us to formulate an
ethical imperative for system designers to promote extrinsic adaptability.
