---
name: domain-identification-grouping
description: Groups existing components into logical business domains to plan service-based architecture. Use when asking "which components belong together?", "group these into services", "organize by domain", "component-to-domain mapping", or planning service extraction from an existing codebase. Do NOT use for identifying new domains from scratch (use domain-analysis) or analyzing coupling (use coupling-analysis).
---

# Domain Identification and Grouping

This skill groups architectural components into logical domains (business areas) to prepare for creating domain services in a service-based architecture.

## How to Use

### Quick Start

Request analysis of your codebase:

- **"Group components into logical domains"**
- **"Identify component domains for service-based architecture"**
- **"Create domain groupings from components"**
- **"Analyze which components belong to which domains"**

### Usage Examples

**Example 1: Domain Identification**

```
User: "Group components into logical domains"

The skill will:
1. Analyze component responsibilities and relationships
2. Identify business domains based on functionality
3. Group components into domains
4. Create domain diagrams
5. Suggest namespace refactoring for domain alignment
```

**Example 2: Domain Analysis**

```
User: "Which domain should the billing components belong to?"

The skill will:
1. Analyze billing component functionality
2. Check relationships with other components
3. Identify appropriate domain (e.g., Customer or Financial)
4. Recommend domain assignment
```

**Example 3: Domain Refactoring**

```
User: "What namespace refactoring is needed to align components with domains?"

The skill will:
1. Compare current component namespaces to identified domains
2. Identify misaligned components
3. Suggest namespace changes
4. Create refactoring plan
```

### Step-by-Step Process

1. **Identify Domains**: Analyze business capabilities and component relationships
2. **Group Components**: Assign components to appropriate domains
3. **Validate Groupings**: Ensure components fit well in their domains
4. **Refactor Namespaces**: Align component namespaces with domains
5. **Create Domain Map**: Visualize domain structure and component groupings

## When to Use

Apply this skill when:

- After identifying, sizing, and analyzing component dependencies
- Before creating domain services (Pattern 6)
- When planning service-based architecture migration
- Analyzing component relationships and business alignment
- Preparing for domain-driven design implementation
- Grouping components for better organization

## Core Concepts

### Domain Definition

A **domain** is a logical grouping of components that:

- Represents a distinct business capability or area
- Contains related components that work together
- Has clear boundaries and responsibilities
- Can become a domain service in service-based architecture

**Examples**:

- **Customer Domain**: Customer profile, billing, support contracts
- **Ticketing Domain**: Ticket creation, assignment, routing, completion
- **Reporting Domain**: Ticket reports, expert reports, financial reports

### Component Domain Relationship

**One-to-Many**: A single domain contains multiple components

```
Domain: Customer
├── Component: Customer Profile
├── Component: Billing Payment
├── Component: Billing History
└── Component: Support Contract
```

### Domain Manifestation

Domains are physically manifested through **namespace structure**:

**Before Domain Alignment**:

```
services/billing/payment
services/billing/history
services/customer/profile
services/supportcontract
```

**After Domain Alignment**:

```
services/customer/billing/payment
services/customer/billing/history
services/customer/profile
services/customer/supportcontract
```

Notice how all customer-related functionality is grouped under `.customer` domain.

## Analysis Process

### Phase 1: Identify Business Domains

Analyze the codebase to identify distinct business domains:

1. **Examine Component Responsibilities**
   - Read component names and descriptions
   - Understand what each component does
   - Identify business capabilities

2. **Look for Business Language**
   - Group components by business vocabulary
   - Example: "billing", "payment", "invoice" → Financial domain
   - Example: "customer", "profile", "contract" → Customer domain

3. **Identify Domain Boundaries**
   - Where do business concepts change?
   - What are the distinct business areas?
   - How do components relate to business capabilities?

4. **Collaborate with Business Stakeholders**
   - Validate domain identification with product owners
   - Ensure domains align with business understanding
   - Get feedback on domain boundaries

**Example Domain Identification**:

```markdown
## Identified Domains

1. **Ticketing Domain** (ss.ticket)
   - Ticket creation, assignment, routing, completion
   - Customer surveys
   - Knowledge base

2. **Customer Domain** (ss.customer)
   - Customer profile
   - Billing and payment
   - Support contracts

3. **Reporting Domain** (ss.reporting)
   - Ticket reports
   - Expert reports
   - Financial reports

4. **Admin Domain** (ss.admin)
   - User maintenance
   - Expert profile management

5. **Shared Domain** (ss.shared)
   - Login
   - Notification
```

### Phase 2: Group Components into Domains

Assign each component to an appropriate domain:

1. **Analyze Component Functionality**
   - What business capability does it support?
   - What domain vocabulary does it use?
   - What other components does it relate to?

2. **Check Component Relationships**
   - Which components are frequently used together?
   - What are the dependencies between components?
   - Do components share data or workflows?

3. **Assign to Domain**
   - Place component in domain that best fits its functionality
   - Ensure component aligns with domain's business language
   - Verify component relationships support domain grouping

4. **Handle Edge Cases**
   - Components that don't fit clearly: Analyze more deeply
   - Components that fit multiple domains: Choose primary domain
   - Shared components: May belong to Shared domain

**Example Component Grouping**:

```markdown
## Component Domain Assignment

### Ticketing Domain (ss.ticket)

- Ticket Shared (ss.ticket.shared)
- Ticket Maintenance (ss.ticket.maintenance)
- Ticket Completion (ss.ticket.completion)
- Ticket Assign (ss.ticket.assign)
- Ticket Route (ss.ticket.route)
- KB Maintenance (ss.ticket.kb.maintenance)
- KB Search (ss.ticket.kb.search)
- Survey (ss.ticket.survey)

### Customer Domain (ss.customer)

- Customer Profile (ss.customer.profile)
- Billing Payment (ss.customer.billing.payment)
- Billing History (ss.customer.billing.history)
- Support Contract (ss.customer.supportcontract)

### Reporting Domain (ss.reporting)

- Reporting Shared (ss.reporting.shared)
- Ticket Reports (ss.reporting.tickets)
- Expert Reports (ss.reporting.experts)
- Financial Reports (ss.reporting.financial)
```

### Phase 3: Validate Domain Groupings

Ensure components fit well in their assigned domains:

1. **Check Cohesion**
   - Do components in domain share business language?
   - Are components frequently used together?
   - Do components have direct relationships?

2. **Verify Boundaries**
   - Are domain boundaries clear?
   - Do components belong to only one domain?
   - Are there components that don't fit anywhere?

3. **Assess Completeness**
   - Are all components assigned to a domain?
   - Are domains cohesive and well-formed?
   - Do domains represent distinct business capabilities?

4. **Get Stakeholder Validation**
   - Review domain groupings with product owners
   - Ensure domains align with business understanding
   - Get feedback on domain boundaries

**Validation Checklist**:

- [ ] All components assigned to a domain
- [ ] Domains have clear boundaries
- [ ] Components fit well in their domains
- [ ] Domains represent distinct business capabilities
- [ ] Stakeholders validate domain groupings

### Phase 4: Refactor Namespaces for Domain Alignment

Align component namespaces with identified domains:

1. **Compare Current vs Target Namespaces**
   - Current: `services/billing/payment`
   - Target: `services/customer/billing/payment`
   - Change: Add `.customer` domain node

2. **Identify Refactoring Needed**
   - Which components need namespace changes?
   - What domain nodes need to be added?
   - Are there components already aligned?

3. **Create Refactoring Plan**
   - List components needing namespace changes
   - Specify target namespace for each
   - Prioritize refactoring work

4. **Execute Refactoring**
   - Update component namespaces
   - Update imports/references
   - Verify all references updated

**Example Namespace Refactoring**:

```markdown
## Namespace Refactoring Plan

### Customer Domain Alignment

| Component        | Current Namespace   | Target Namespace            | Action        |
| ---------------- | ------------------- | --------------------------- | ------------- |
| Billing Payment  | ss.billing.payment  | ss.customer.billing.payment | Add .customer |
| Billing History  | ss.billing.history  | ss.customer.billing.history | Add .customer |
| Customer Profile | ss.customer.profile | ss.customer.profile         | No change     |
| Support Contract | ss.supportcontract  | ss.customer.supportcontract | Add .customer |

### Ticketing Domain Alignment

| Component      | Current Namespace | Target Namespace         | Action      |
| -------------- | ----------------- | ------------------------ | ----------- |
| KB Maintenance | ss.kb.maintenance | ss.ticket.kb.maintenance | Add .ticket |
| KB Search      | ss.kb.search      | ss.ticket.kb.search      | Add .ticket |
| Survey         | ss.survey         | ss.ticket.survey         | Add .ticket |
```

### Phase 5: Create Domain Map

Visualize domain structure and component groupings:

1. **Create Domain Diagram**
   - Show domains as boxes
   - Show components within each domain
   - Show relationships between domains

2. **Document Domain Structure**
   - List domains and their components
   - Describe domain responsibilities
   - Note domain boundaries

3. **Create Domain Inventory**
   - Table of domains and components
   - Component counts per domain
   - Size metrics per domain

**Example Domain Map**:

```markdown
## Domain Map
```

┌─────────────────────────────────────┐
│ Ticketing Domain (ss.ticket) │
├─────────────────────────────────────┤
│ • Ticket Shared │
│ • Ticket Maintenance │
│ • Ticket Completion │
│ • Ticket Assign │
│ • Ticket Route │
│ • KB Maintenance │
│ • KB Search │
│ • Survey │
└─────────────────────────────────────┘
│
│ uses
▼
┌─────────────────────────────────────┐
│ Customer Domain (ss.customer) │
├─────────────────────────────────────┤
│ • Customer Profile │
│ • Billing Payment │
│ • Billing History │
│ • Support Contract │
└─────────────────────────────────────┘

````

## Output Format

### Domain Identification Report

```markdown
## Domain Identification

### Domain: Customer (ss.customer)

**Business Capability**: Manages customer relationships, billing, and support contracts

**Components**:
- Customer Profile (ss.customer.profile)
- Billing Payment (ss.customer.billing.payment)
- Billing History (ss.customer.billing.history)
- Support Contract (ss.customer.supportcontract)

**Component Count**: 4
**Total Size**: ~15,000 statements (18% of codebase)

**Domain Cohesion**: ✅ High
- Components share customer-related vocabulary
- Components frequently used together
- Direct relationships between components

**Boundaries**:
- Clear separation from Ticketing domain
- Clear separation from Reporting domain
- Shared components (Notification) used by all domains
````

### Component Domain Assignment Table

```markdown
## Component Domain Assignment

| Component          | Current Namespace     | Assigned Domain | Target Namespace                  |
| ------------------ | --------------------- | --------------- | --------------------------------- |
| Customer Profile   | ss.customer.profile   | Customer        | ss.customer.profile (no change)   |
| Billing Payment    | ss.billing.payment    | Customer        | ss.customer.billing.payment       |
| Ticket Maintenance | ss.ticket.maintenance | Ticketing       | ss.ticket.maintenance (no change) |
| KB Maintenance     | ss.kb.maintenance     | Ticketing       | ss.ticket.kb.maintenance          |
| Reporting Shared   | ss.reporting.shared   | Reporting       | ss.reporting.shared (no change)   |
```

### Namespace Refactoring Plan

```markdown
## Namespace Refactoring Plan

### Priority: High

**Customer Domain Alignment**

**Components to Refactor**:

1. Billing Payment: `ss.billing.payment` → `ss.customer.billing.payment`
2. Billing History: `ss.billing.history` → `ss.customer.billing.history`
3. Support Contract: `ss.supportcontract` → `ss.customer.supportcontract`

**Steps**:

1. Update namespace declarations in source files
2. Update import statements in dependent components
3. Update directory structure
4. Run tests to verify changes
5. Update documentation

**Expected Impact**:

- All customer-related components aligned under `.customer` domain
- Clearer domain boundaries
- Easier to identify domain components
```

### Domain Map Visualization

```markdown
## Domain Map

### Domain Structure
```

Customer Domain (ss.customer)
├── Customer Profile
├── Billing Payment
├── Billing History
└── Support Contract

Ticketing Domain (ss.ticket)
├── Ticket Shared
├── Ticket Maintenance
├── Ticket Completion
├── Ticket Assign
├── Ticket Route
├── KB Maintenance
├── KB Search
└── Survey

Reporting Domain (ss.reporting)
├── Reporting Shared
├── Ticket Reports
├── Expert Reports
└── Financial Reports

Admin Domain (ss.admin)
├── User Maintenance
└── Expert Profile

Shared Domain (ss.shared)
├── Login
└── Notification

```

### Domain Relationships

```

Ticketing Domain
│ uses
├─→ Shared Domain (Login, Notification)
└─→ Customer Domain (Customer Profile)

Customer Domain
│ uses
└─→ Shared Domain (Login, Notification)

Reporting Domain
│ uses
├─→ Ticketing Domain (Ticket data)
├─→ Customer Domain (Customer data)
└─→ Shared Domain (Login)

```

```

## Analysis Checklist

**Domain Identification**:

- [ ] Analyzed component responsibilities
- [ ] Identified business capabilities
- [ ] Identified distinct business domains
- [ ] Validated domains with stakeholders

**Component Grouping**:

- [ ] Assigned each component to a domain
- [ ] Analyzed component relationships
- [ ] Ensured components fit domain vocabulary
- [ ] Handled edge cases (shared components, unclear assignments)

**Domain Validation**:

- [ ] Checked cohesion within domains
- [ ] Verified domain boundaries are clear
- [ ] Ensured all components assigned
- [ ] Validated with stakeholders

**Namespace Refactoring**:

- [ ] Compared current vs target namespaces
- [ ] Identified components needing refactoring
- [ ] Created refactoring plan
- [ ] Prioritized refactoring work

**Domain Mapping**:

- [ ] Created domain diagram
- [ ] Documented domain structure
- [ ] Created domain inventory table
- [ ] Documented domain relationships

## Implementation Notes

### For Node.js/Express Applications

Domains typically organized in `services/` directory:

```
services/
├── customer/              ← Customer Domain
│   ├── profile/
│   ├── billing/
│   │   ├── payment/
│   │   └── history/
│   └── supportcontract/
├── ticket/                ← Ticketing Domain
│   ├── shared/
│   ├── maintenance/
│   ├── assign/
│   └── route/
└── reporting/             ← Reporting Domain
    ├── shared/
    ├── tickets/
    └── experts/
```

### For Java Applications

Domains identified by package structure:

```
com.company.customer       ← Customer Domain
├── profile
├── billing
│   ├── payment
│   └── history
└── supportcontract

com.company.ticket         ← Ticketing Domain
├── shared
├── maintenance
├── assign
└── route
```

### Domain Identification Strategies

**Strategy 1: Business Capability Analysis**

- Identify what business capabilities the system provides
- Group components by capability
- Example: "Customer Management" capability → Customer Domain

**Strategy 2: Vocabulary Analysis**

- Identify business vocabulary used by components
- Group components sharing same vocabulary
- Example: Components using "billing", "payment", "invoice" → Financial Domain

**Strategy 3: Relationship Analysis**

- Identify components frequently used together
- Group components with strong relationships
- Example: Components that share data/workflows → Same Domain

**Strategy 4: Stakeholder Collaboration**

- Work with product owners/business analysts
- Use their understanding of business areas
- Validate domain boundaries with them

## Fitness Functions

After creating domains, create automated checks:

### Domain Namespace Governance

```javascript
// Ensure components belong to correct domain
function validateDomainNamespaces(components, domainRules) {
  const violations = []

  components.forEach((comp) => {
    const domain = identifyDomain(comp.namespace)
    const expectedDomain = domainRules[comp.name]

    if (domain !== expectedDomain) {
      violations.push({
        component: comp.name,
        currentDomain: domain,
        expectedDomain: expectedDomain,
        namespace: comp.namespace,
      })
    }
  })

  return violations
}
```

### Domain Boundary Enforcement

```javascript
// Prevent components from accessing other domains directly
function enforceDomainBoundaries(components) {
  const violations = []

  components.forEach((comp) => {
    comp.imports.forEach((imp) => {
      const importedDomain = identifyDomain(imp)
      const componentDomain = identifyDomain(comp.namespace)

      if (importedDomain !== componentDomain && importedDomain !== 'shared') {
        violations.push({
          component: comp.name,
          domain: componentDomain,
          importsFrom: imp,
          importedDomain: importedDomain,
          issue: 'Cross-domain direct dependency',
        })
      }
    })
  })

  return violations
}
```

## Best Practices

### Do's ✅

- Collaborate with business stakeholders to identify domains
- Group components by business capability, not technical layers
- Ensure domains represent distinct business areas
- Validate domain boundaries with stakeholders
- Refactor namespaces to align with domains
- Create clear domain documentation
- Use business language in domain names

### Don'ts ❌

- Don't create domains based on technical layers (services, controllers, models)
- Don't force components into domains where they don't fit
- Don't skip stakeholder validation
- Don't create too many small domains (aim for 3-7 domains)
- Don't create domains that are too large (monolithic domains)
- Don't ignore components that don't fit (analyze why)
- Don't skip namespace refactoring (critical for clarity)

## Common Domain Patterns

### Typical Domains in Business Applications

- **Customer Domain**: Customer management, profiles, relationships
- **Product Domain**: Product catalog, inventory, pricing
- **Order Domain**: Order processing, fulfillment, shipping
- **Billing Domain**: Invoicing, payments, financial transactions
- **Reporting Domain**: Reports, analytics, dashboards
- **Admin Domain**: User management, system configuration
- **Shared Domain**: Common functionality (login, notification, utilities)

### Domain Size Guidelines

- **Small Domain**: 2-4 components
- **Medium Domain**: 5-8 components
- **Large Domain**: 9-15 components
- **Too Large**: >15 components (consider splitting)

## Next Steps

After creating component domains:

1. **Apply Create Domain Services Pattern** - Extract domains to separate services
2. **Plan Service Extraction** - Create migration plan for domain services
3. **Implement Domain Services** - Move domains to separately deployed services
4. **Monitor Domain Boundaries** - Use fitness functions to enforce boundaries

## Notes

- Domains should represent business capabilities, not technical layers
- Domain identification requires collaboration with business stakeholders
- Namespace refactoring is critical for domain clarity
- Domains prepare the codebase for service-based architecture
- Well-formed domains make service extraction easier
- Domain boundaries should be clear and well-documented