The Heart of Software

The heart of software is its ability to solve domain-related problems for its user. All other features, vital though they may be, support this basic purpose. When the domain is complex, this is a difficult task, calling for the concentrated effort of talented and skilled people. Developers have to steep themselves in the domain to build up knowledge of the business. They must hone their modeling skills and master domain design.

Yet these are not the priorities on most software projects. Most talented developers do not have much interest in learning about the specific domain in which they are working, much less making a major commitment to expand their domain-modeling skills. Technical people enjoy quantifiable problems that exercise their technical skills. Domain work is messy and demands a lot of complicated new knowledge that doesn't seem to add to a computer scientist's capabilities.

Instead, the technical talent goes to work on elaborate frame-works, trying to solve domain problems with technology. Learning about and modeling the domain is left to others. Complexity in the heart of software has to be tackled head-on. To do otherwise is to risk irrelevance.

In a TV talk show interview, comedian John Cleese told a story of an event during the filming of Monty Python and the Holy Grail. They had been shooting a particular scene over and over, but somehow it wasn't funny. Finally, he took a break and consulted with fellow comedian Michael Palin (the other actor in the scene), and they came up with a slight variation. They shot one more take, and it turned out funny, so they called it a day.

The next morning, Cleese was looking at the rough cut the film editor had put together of the previous day's work. Coming to the scene they had struggled with, Cleese found that it wasn't funny; one of the earlier takes had been used.

He asked the film editor why he hadn't used the last take, as directed. “Couldn't use it. Someone walked in-shot,” the editor replied. Cleese watched the scene again, and then again. Still he could see nothing wrong. Finally, the editor stopped the film and pointed out a coat sleeve that was visible for a moment at the edge of the picture.

Eric Evans - Domain-driven design: Tackling Complexity in the Heart of Software, 2003