Creating architectures with building blocks

Large systems need a sound architecture. In our method, we decompose the system into building blocks to make it "future-proof," accommodate functional needs, and minimize system complexity. We organize the system construction along three design dimensions covered by the system architecture: structure, aspects, and behavior. The structure determines the system's decomposition into parts and the relationships between the parts. Aspects model the functional decomposition of the system. Behavior deals with processing that takes place within the system. Of the three dimensions, we consider structure to be the most important. In this dimension, reducing complexity is our main concern. We organize system functionality into four layers, or subsystems. These subsystems are composed of software modules-building blocks-which are the basic software entities in the system architecture.<>