APPLY

Describe a system or process

Show boundaries, relationships, order, and state without mixing them.

Start here

Architecture & structure · Model

C4 model

Explain a software architecture through a small set of consistent levels of detail.

Introductory

Start with the system boundary and its neighbors when the question is what exists. Use a sequence view for who calls whom over time, or BPMN when organizational handoffs and workflow events are the central question.

This recommendation fits when

You need a software-system overview, with optional deeper behavior views.

Choose differently when

For a non-software organizational workflow, start with BPMN instead. C4 alone does not establish runtime order or business policy.

A practical route

Write the exact question the view should answer.
Choose the boundary and level of detail.
Label responsibilities and relationships.
Add a separate behavior view only when the question needs it.

Useful companions

Architecture & structure · Modeling language

UML

Choose a defined notation for structure, interactions, activities, or state changes.

Intermediate

Requirements & behavior · Standard notation

BPMN

Describe a business process through activities, events, decisions, and participant boundaries.

Intermediate

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This is an editorial recommendation for the stated situation. It is not a personalized diagnosis or a ranking of all methods.