What Is Architecture?
In a conversation we once had with Grady Booch, he said, “Every software system has an architecture, regardless of whether the architecture was developed intentionally. The bigger question is whether it is a good architecture.”
The textbook definition of architecture is
Architecture:
1. The art or science of building; specifically: the art or practice of designing and building structures and especially habitable ones.
1a: Formation or construction as or as if as the result of conscious act <the architecture of the garden>.
2. The manner in which the components of a computer or computer system are organized and integrated. [MEWE1]
An architecture depicts how something's parts come together to form a whole. An airplane has an architecture; this book has an architecture—even your body has an architecture, although their characteristics vary. If you are going to build something, it is quite helpful to describe its architecture, either textually, as in the outline of a book before writing it, or by modeling what that thing will look like (see Figure 4-1).
Figure 4-1. A partial view of an airplane's architectural drawing.
For the purposes of this book, an architecture is the structure of a system. The architecture incorporates the business rules, the software, and how the software will communicate with other pieces of software. An architecture can include software both inside and outside of your organization. Because your internal systems might need to be integrated with partners, customers, and vendors, your architecture can be made up of internal and external systems. It also can include the hardware on which the software runs, and it might even include an understanding and description of who will use the system and how it will be used.