arc42-documentation

What this skill does

# arc42 Documentation Skill

## When to Use This Skill

Use this skill when:

- **Arc42 Documentation tasks** - Working on arc42 architecture documentation template and guidance
- **Planning or design** - Need guidance on Arc42 Documentation approaches
- **Best practices** - Want to follow established patterns and standards

## Overview

Create comprehensive architecture documentation using the arc42 template.

## MANDATORY: Documentation-First Approach

Before creating arc42 documentation:

1. **Invoke `docs-management` skill** for architecture documentation patterns
2. **Verify arc42 current version** via MCP servers (perplexity)
3. **Base guidance on official arc42 template**

## arc42 Template Structure

```text
arc42 Template (12 Sections):

┌─────────────────────────────────────────────────────────────────────────────┐
│  1. Introduction and Goals                                                   │
│     Requirements overview, quality goals, stakeholders                       │
├─────────────────────────────────────────────────────────────────────────────┤
│  2. Architecture Constraints                                                 │
│     Technical, organizational, and convention constraints                    │
├─────────────────────────────────────────────────────────────────────────────┤
│  3. System Scope and Context                                                 │
│     Business context, technical context                                      │
├─────────────────────────────────────────────────────────────────────────────┤
│  4. Solution Strategy                                                        │
│     Technology decisions, top-level decomposition, quality approaches        │
├─────────────────────────────────────────────────────────────────────────────┤
│  5. Building Block View                                                      │
│     Static decomposition: whitebox/blackbox at multiple levels               │
├─────────────────────────────────────────────────────────────────────────────┤
│  6. Runtime View                                                             │
│     Important scenarios, interactions, behaviors                             │
├─────────────────────────────────────────────────────────────────────────────┤
│  7. Deployment View                                                          │
│     Technical infrastructure, mapping of building blocks                     │
├─────────────────────────────────────────────────────────────────────────────┤
│  8. Cross-cutting Concepts                                                   │
│     Recurring patterns, approaches, principles                               │
├─────────────────────────────────────────────────────────────────────────────┤
│  9. Architecture Decisions                                                   │
│     Important decisions with rationale (may link to ADRs)                    │
├─────────────────────────────────────────────────────────────────────────────┤
│ 10. Quality Requirements                                                     │
│     Quality tree, quality scenarios                                          │
├─────────────────────────────────────────────────────────────────────────────┤
│ 11. Risks and Technical Debt                                                 │
│     Known risks, technical debt items                                        │
├─────────────────────────────────────────────────────────────────────────────┤
│ 12. Glossary                                                                 │
│     Important domain and technical terms                                     │
└─────────────────────────────────────────────────────────────────────────────┘
```

## Complete arc42 Template

```markdown
# Architecture Documentation: [System Name]

**Version:** 1.0
**Date:** [Date]
**Status:** Draft | Review | Final

---

## 1. Introduction and Goals

### 1.1 Requirements Overview

[Brief description of the system and its purpose. What business problem
does it solve? Who are the main users?]

**Key Features:**
- [Feature 1]
- [Feature 2]
- [Feature 3]

### 1.2 Quality Goals

| Priority | Quality Goal | Description |
|----------|--------------|-------------|
| 1 | [Goal] | [Description] |
| 2 | [Goal] | [Description] |
| 3 | [Goal] | [Description] |

### 1.3 Stakeholders

| Role | Name/Team | Expectations |
|------|-----------|--------------|
| Product Owner | [Name] | [Expectations] |
| Development Team | [Team] | [Expectations] |
| Operations | [Team] | [Expectations] |
| Security | [Team] | [Expectations] |

---

## 2. Architecture Constraints

### 2.1 Technical Constraints

| Constraint | Description | Background |
|------------|-------------|------------|
| [TC-1] | [Description] | [Why this constraint exists] |
| [TC-2] | [Description] | [Why this constraint exists] |

### 2.2 Organizational Constraints

| Constraint | Description | Background |
|------------|-------------|------------|
| [OC-1] | [Description] | [Why this constraint exists] |
| [OC-2] | [Description] | [Why this constraint exists] |

### 2.3 Conventions

| Convention | Description |
|------------|-------------|
| [CON-1] | [Description] |
| [CON-2] | [Description] |

---

## 3. System Scope and Context

### 3.1 Business Context

[Diagram showing the system in its business environment, with actors
and external systems it interacts with.]

```mermaid
C4Context
    title System Context Diagram

    Person(user, "User", "End user of the system")
    System(system, "System Name", "System description")
    System_Ext(ext1, "External System 1", "Description")
    System_Ext(ext2, "External System 2", "Description")

    Rel(user, system, "Uses")
    Rel(system, ext1, "Calls API")
    Rel(system, ext2, "Sends events")
```

| Actor/System | Description | Communication |
|--------------|-------------|---------------|
| [Actor 1] | [Description] | [Protocol/Format] |
| [External System 1] | [Description] | [Protocol/Format] |

### 3.2 Technical Context

[Technical details of integration: protocols, data formats, interfaces.]

| Interface | Technology | Description |
|-----------|------------|-------------|
| [API 1] | REST/JSON | [Description] |
| [Queue 1] | Kafka | [Description] |
| [File 1] | SFTP/CSV | [Description] |

---

## 4. Solution Strategy

### 4.1 Technology Decisions

| Decision | Technology | Rationale |
|----------|------------|-----------|
| Programming Language | C# (.NET 10) | [Rationale] |
| Database | PostgreSQL | [Rationale] |
| Message Broker | Kafka | [Rationale] |
| Cloud Platform | Azure | [Rationale] |

### 4.2 Top-Level Decomposition

[High-level description of how the system is structured.]

**Approach:** [Microservices / Modular Monolith / etc.]

**Key Modules:**

### 4.3 Approaches to Achieve Quality Goals

| Quality Goal | Approach |
|--------------|----------|
| Performance | Caching, async processing, optimized queries |
| Reliability | Redundancy, circuit breakers, retry patterns |
| Security | Defense in depth, encryption, audit logging |

---

## 5. Building Block View

### 5.1 Level 1: Whitebox Overall System

```mermaid
C4Container
    title Container Diagram

    Container(api, "API Gateway", "Kong", "Routes and secures API calls")
    Container(web, "Web Application", "Blazor", "User interface")
    Container(svc1, "Service 1", ".NET", "Business logic")
    Container(svc2, "Service 2", ".NET", "Business logic")
    ContainerDb(db, "Database", "PostgreSQL", "Stores data")
    ContainerQueue(queue, "Message Queue", "Kafka", "Async messaging")

    Rel(web, api, "Calls", "HTTPS")
    Rel(api, svc1, "Forwards", "gRPC")
    Rel(api, svc2, "Forwards", "gRPC")
    Rel(svc1, db, "Reads/Writes")
    Rel(svc1, queue, "Publishes")
    Rel(svc2, queue, "Subscribes")
```

**Contained Building Blocks:**

| Building Block | Purpose |
|----------------|---------|
| API Gateway | Request routing, authentication, rate limiting |
| Web Application | Us