C H A P T E R  5

Software Architecture

What do we mean by a software architecture? To me the term architecture conveys a notion of the core elements of the system, the pieces that are difficult to change. A foundation on which the rest must be built.

—Martin Fowler¹

Once you have an idea of what you're going to build, then you can start thinking about how you're going to build it. Of course, you've already been thinking about this from the very first requirement, but now you have permission to do it. Now we begin to delve into design.

There are really two levels of software design. The level we normally think of when we're writing programs is usually called detailed design. What operations do we need? What data structures? What algorithms are we using? How is the database going to be organized? What does the user interface look like? What are the calling sequences? These are all very detailed questions that need to be answered before you can really get on with the detailed work of coding (well, sort of – we'll get to that later).