---
id: wiki-2026-0508-c4-modeling-framework
title: C4 Modeling Framework
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [C4 Model, C4 Diagrams, Simon Brown C4]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [architecture, c4, diagram, structurizr, documentation]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: DSL
  framework: Structurizr
---

# C4 Modeling Framework

## 매 한 줄
> **"매 software architecture = 4 zoom levels (Context → Container → Component → Code)."**. 매 Simon Brown 이 2006년경 제안한 lightweight visualization framework. 매 2026 현재 Structurizr DSL + Mermaid C4 plugin 으로 diagram-as-code 가 standard, 매 audience-specific abstraction level 이 핵심 가치.

## 매 핵심

### 매 4 levels
- **L1 — System Context**: 매 system + users + external systems. 매 non-technical stakeholder 용.
- **L2 — Container**: 매 deployable unit (web app, API, DB, queue). 매 technical lead 용.
- **L3 — Component**: 매 container 내부 logical grouping (controller, service, repo). 매 dev team 용.
- **L4 — Code**: 매 class diagram (UML). 매 거의 안 그림 — IDE 가 대신.

### 매 supplementary diagrams
- **Deployment diagram**: 매 container → infrastructure node mapping.
- **Dynamic diagram**: 매 runtime sequence/collaboration.
- **System landscape**: 매 enterprise-wide multi-system view.

### 매 응용
1. **Onboarding doc**: 매 새 dev 의 codebase orientation.
2. **ADR illustration**: 매 architecture decision record 의 visual aid.
3. **Stakeholder communication**: 매 PM/exec 에게 system scope 설명.
4. **Compliance audit**: 매 data flow / boundary 시각화.

## 💻 패턴

### Structurizr DSL (canonical)
```dsl
workspace "Banking System" {
  model {
    customer = person "Customer"
    bankSystem = softwareSystem "Internet Banking" {
      webApp = container "Web Application" "Spring Boot" "Java"
      mobileApp = container "Mobile App" "React Native" "TypeScript"
      api = container "API" "Spring Boot" "Java"
      db = container "Database" "PostgreSQL" "RDBMS"

      webApp -> api "uses" "JSON/HTTPS"
      mobileApp -> api "uses" "JSON/HTTPS"
      api -> db "reads/writes" "JDBC"
    }
    mainframe = softwareSystem "Mainframe" "External"
    customer -> bankSystem "uses"
    bankSystem -> mainframe "fetches account data" "MQ"
  }
  views {
    systemContext bankSystem { include * autolayout }
    container bankSystem { include * autolayout }
    theme default
  }
}
```

### Mermaid C4 (in-repo markdown)
```mermaid
C4Context
  title System Context — Banking
  Person(customer, "Customer")
  System(bank, "Internet Banking", "Allows customers to view accounts")
  System_Ext(mainframe, "Mainframe", "Legacy core banking")
  Rel(customer, bank, "Uses")
  Rel(bank, mainframe, "Fetches data", "MQ")
```

### Component-level decomposition
```dsl
api = container "API" {
  signInController = component "SignIn Controller" "Spring MVC"
  accountsController = component "Accounts Controller" "Spring MVC"
  authService = component "Auth Service" "Spring Bean"
  accountsRepo = component "Accounts Repository" "Spring Data JPA"

  signInController -> authService "uses"
  accountsController -> accountsRepo "reads"
  authService -> db "verifies credentials"
}
```

### Deployment view
```dsl
deploymentEnvironment "Production" {
  deploymentNode "AWS us-east-1" {
    deploymentNode "EKS Cluster" {
      containerInstance webApp
      containerInstance api
    }
    deploymentNode "RDS" {
      containerInstance db
    }
  }
}
```

### Generated docs pipeline
```bash
# CI step — render diagrams from DSL
docker run --rm -v $PWD:/usr/local/structurizr structurizr/cli \
  export -workspace workspace.dsl -format plantuml/c4plantuml
plantuml -tsvg *.puml
mv *.svg docs/architecture/
```

### ADR + C4 link
```markdown
# ADR-007: Move auth to dedicated service
**Status**: Accepted
**Context**: See [Container diagram](../diagrams/banking-containers.svg)
**Decision**: Extract `authService` component into its own container.
**Consequences**: New diagram in `diagrams/v2-containers.svg`.
```

## 매 결정 기준
| 상황 | Diagram level |
|---|---|
| Pitch to exec / new joiner intro | L1 Context |
| Tech selection / deployment plan | L2 Container |
| Code review / refactor discussion | L3 Component |
| Inheritance question | IDE (skip L4) |
| Multi-system enterprise view | System Landscape |

**기본값**: L1 + L2 (둘만 있어도 90% communication 충족).

## 🔗 Graph
- 부모: [[Software_Architecture]] · [[Architecture_Documentation]]
- 변형: [[arc42]]
- 응용: [[ADR]] · [[Structurizr]]
- Adjacent: [[Mermaid]] · [[PlantUML]] · [[DDD]]

## 🤖 LLM 활용
**언제**: greenfield architecture 문서화, legacy reverse-engineering, ADR illustration.
**언제 X**: real-time runtime monitoring (observability tool 영역).

## ❌ 안티패턴
- **All 4 levels for every system**: 매 L4 거의 무의미 — IDE 대체.
- **Mixing levels in one diagram**: 매 abstraction 깨짐 → audience 혼란.
- **No legend / inconsistent shapes**: 매 reader 가 element type 못 구분.
- **Diagram drift**: 매 DSL 없이 manual draw → 6개월 후 stale.

## 🧪 검증 / 중복
- Verified (c4model.com — Simon Brown, Structurizr DSL spec 2024).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — C4 levels, Structurizr DSL, Mermaid C4 examples |