Martin Fowler wrote an important book in the canon of software engineering more than 20 years ago. In it, he attempted to distill the ways that existing software can be improved. Since then, he has published a second edition and now, an online one as well. Though he didn’t invent the term, his book helped popularize “refactoring” and it is used even among non-professionals to refer to any kind of maintenance or upkeep activity. In elementary algebra, the term “factoring” refers to finding a multiplier that can be extracted from an algebraic expression without changing its veracity, often as part of a process of solving an equation. Similarly, refactoring in software is the practice of identifying ways that the code can be changed for the better without altering its functionality.
Though it may seem counter-intuitive that a purely intellectual abstraction like software code can deteriorate, as if it were a physical object, in fact, software constantly atrophies. It atrophies in several ways:
- Context change: even software that is functioning perfectly well must live in an environment that itself is changing. In this way, relative to its environment, the software has changed, often in ways that reduce its functionality or make it completely unable to perform its prescribed task.
- Functionality change: in the…