The Software Architect Elevator

Chapter 23. Drawing the Line

Architecture Without Lines Likely Isn’t One

A functional architecture of a car

The sketch above depicts the architecture of a car. All the important components are there, including their relationships: the engine is under the hood; passenger seats are appropriately located inside the passenger compartment, close to the steering wheel; wheels are assembled nicely at the bottom of the car in the chassis. This diagram appears to fulfill most definitions of architecture (except my favorite one because I am looking for decisions; see Chapter 8).

However, it does precious little to help you understand how a car functions: could you omit the gas tank because it’s far away from the engine, anyway? Are engine and transmission side by side under the hood by coincidence or do they have a special relationship? Does the car need exactly four wheels or will three also do? If you had to build the car in stages, what subset would make sense to assemble first? Would just the cabin with the seats be a good start? How can you distinguish a good car from a bad one? Which aspects are common in virtually all cars (e.g., the wheels being at the bottom) and which ones vary (Porsche 911, VW Beetle, or DeLorean owners would be quick to point out that their engine isn’t under the hood)?

The picture doesn’t really answer any of these questions. It depicts the location of the ...