You heard it here first.

Extreme Decomposition (XD) is a term that I believe that I coined a few years ago and I've still not seen it used anywhere, so I'm staking my claim to it officially here.

XD is a concept of designing software where functionality is broken down iteratively until it is completely decomposed into "atomic" items that serve a single unit of functionality in a system.  Each of these items must be able to be independently coded and tested to be a viable component of a software system.

Through this building of many atomic and properly functioning components to a system, they can then be reliably reused as subcomponents of higher level abstractions in the system, each of which must be individually tested themselves by building new tests that the test both the new functionality that integrates the child components.

Therefore by building a system of atomic components glued together then we can rapidly build new systems that meet the reliability and agility required in todays world.

For more information, please visit xDecomp.info.