The story of software architecture reminds me of the following story.
“A well-known scientist (some say it was Bertrand Russell) once gave a public lecture on astronomy. He described how the earth orbits around the sun and how the sun, in turn, orbits around the center of a vast collection of stars called our galaxy. At the end of the lecture, a little old lady at the back of the room got up and said: “What you have told us is rubbish. The world is really a flat plate supported on the back of a giant tortoise.” The scientist gave a superior smile before replying, “What is the tortoise standing on?” “You’re very clever, young man, very clever”, said the old lady. “But it’s turtles all the way down!”
– A Brief History of Time by Stephen Hawking
Software architecture is “‘turtles all the way down.”
The Ivory Tower
Many of us can relate. In dysfunctional organizations, architects and developers fail to communicate effectively. The result is a lack of transparency and a lack of understanding by both sides, as shown in the diagrm (click to enlarge). The failure often occurs (though I recognize there are other causes) because architecture is about breadth and development is about depth. Each group has disparate views of software architecture, and while both are warranted, a gap between these views exists. The architect might focus on applications and services while the developer focuses on the code. Sadly, there is a lot in between that nobody is focused on. It is this gap between breadth and depth that contributes to ivory tower architecture.
Turtles and The Tower
Without question, the ivory tower is dysfunctional (regardless of cause), and systems lacking architectural integrity are a symptom of ivory tower architecture. So assuming good intent on the part of the architect and the developer, how can we bridge the gap between breadth and depth? How can we communicate more effectively? How do we increase understanding and transparency?
My favorite definition of software architecture was offered by Ralph Johnson in an article by Martin Fowler. He states:
In most successful software projects, the expert developers working on that project have a shared understanding of the system design. This shared understanding is called ‘architecture.’ This understanding includes how the system is divided into components and how the components interact through interfaces. These components are usually composed of smaller components, but the architecture only includes the components and interfaces that are understood by all the developers…Architecture is about the important stuff. Whatever that is.
The key aspect of this definition that differentiates it from many other definitions of architecture is that of “shared understanding.” We must have a shared understanding of how the system is divided into components, and how they interact. Architecture isn’t just some technical concept, but also a social construct. And it is through this that we can break down the divide between architects and developers.
To ensure shared understanding, we have to architect “all the way down.” Architects cannot worry only about services and developers cannot worry only about code. There is a huge middle ground that each must also focus on, as illustrated by the diagram at right (click to enlarge).
Focusing exclusively on top level abstractions is not enough. Emphasizing only code quality is not enough either. We must bridge the gap through other means, including module and package design. Often times, when I speak, I ask the audience to raise their hands if they spend time on service design. Most do. I also ask them to raise their hand if they spend time on class design and code quality. Again, most do. But then I ask if they also spend time on package and module design. Usually, only a small percentage leave their hands raised.
This is unfortunate, because module and package design are equally as important as service and class design. But somewhere along the way, with our emphasis on services and code quality, we’ve lost sight of what lies in between. Within each application or service awaits a rotting design, and atop even the most flexible code sits a suite of applications or services riddled with duplication and lack of understanding. A resilient package structure and corresponding software modules help bridge the divide between services and code.
Certainly, if I’ve said it once, I’ve said it at least a few times, we need to start focusing on modularity to ensure a consistent architecture story is told. It is the glue that binds. It’s the piece that helps bridge low level class design with higher level service design. It’s the piece that helps bring down the ivory tower, enhance communication, increase transparency, ensure understanding, and verify consistency at multiple levels. It is the piece that allows us to “architect all the way down.”