Appendix C. C4 Model

The C4 model ( is a system architecture diagram technique created by Simon Brown to decompose a system into various levels of abstraction. This section is a brief introduction to the C4 model. The website has good introductions and in-depth coverage of the C4 model, so we will only briefly go over the C4 model here; readers should refer to the website for more details. The C4 model defines four levels of abstraction.

A context diagram represents the system as a single box, surrounded by its users and other systems that it interacts with. Figure C.1 is an example context diagram of a new internet banking system that we wish to design on top of our existing mainframe banking system. Its users will be our ...

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