The C4 model is a lean graphical notation technique for modeling the architecture of software systems.[1][2] It is based on a structural decomposition (a hierarchical tree structure) of a system into containers and components and relies on existing modelling techniques such as Unified Modeling Language (UML) or entity–relationship diagrams (ERDs) for the more detailed decomposition of the architectural building blocks.
some standard are emerging for diagramming software architecture (such as software architect Simon Brown's C4 model or The Open Group Archimate standard)