Programming as Theory Building

Picture, you join a new team working on a big system. Everybody who knew anything has left, either to find greener grass or to enjoy a well deserved pension. You and the team struggle to build new features for the system or to adapt functionality to match changes in legislation. Not to mention the trouble it is to figure out what to fix when things go wrong. At the same time, the business that you support is screaming for innovation and pushing for more and more changes. Recognize this situation? Ever experienced it yourself? A world full of legacy systems “Legacy. What is a legacy? It’s planting seeds in a garden you never get to see.” – Lin-Manuel Miranda, “Hamilton” Legacy, the thing that you are remembered for, typically the word has a positive meaning… how come that in tech the word “Legacy” has such a bad connotation? When we call out a legacy system, we usually mean: code without tests ( Michael Feathers ) or code you “got” from somebody else, or code that you’re scared to touch. However, there is a reason these legacy systems are still around. In almost all cases, that system still brings in money or is somehow still valuable. If it did not bring any value anymore, wouldn’t it be decommissioned? There must be something in these systems that makes them survive, where other systems did not. How systems become “Legacy” So legacy systems are those that have become hard or scary to change. In my experience, that not because something is wrong with the code or technology. The major contributing factor is usually that the knowledge about the system has left the organization. And then I don’t mean the documentation, but the people that built, maintained and ran the system. When those people are gone, you know that nobody else is going to be happy touching that thing. The value of software Code is like a mapping of desired real world behavior to a program that can be executed by a machine. So where is the value of a system, is that in that code? Over the past years I