Domain Analysis

Subdomain Identification & Bounded Context Analysis

This skill analyzes codebases to identify subdomains (Core, Supporting, Generic) and suggest bounded contexts following Domain-Driven Design Strategic Design principles.

When to Use

Apply this skill when:

• Analyzing domain boundaries in any codebase
• Identifying Core, Supporting, and Generic subdomains
• Mapping bounded contexts from problem space to solution space
• Assessing domain cohesion and detecting coupling issues
• Planning domain-driven refactoring
• Understanding business capabilities in code

Core Principles

Subdomain Classification

Core Domain: Competitive advantage, highest business value, requires best developers

• Indicators: Complex business logic, frequent changes, domain experts needed

Supporting Subdomain: Essential but not differentiating, business-specific

• Indicators: Supports Core Domain, moderate complexity, business-specific rules

Generic Subdomain: Common functionality, could be outsourced

• Indicators: Well-understood problem, low differentiation, standard functionality

Bounded Context

An explicit linguistic boundary where domain terms have specific, unambiguous meanings.

• Primary nature: Linguistic boundary, not technical
• Key rule: Inside boundary, all Ubiquitous Language terms are unambiguous
• Goal: Align 1 subdomain to 1 bounded context (ideal)

Analysis Process

Phase 1: Extract Concepts

Scan codebase for business concepts (not infrastructure):

1. Entities (domain models with identity)

   • Patterns: @Entity, class, domain models
   • Focus: Business concepts, not technical classes

2. Services (business operations)

   • Patterns: *Service, *Manager, *Handler
   • Focus: Business logic, not technical utilities

3. Use Cases (business workflows)

   • Patterns: *UseCase, *Command, *Handler
   • Focus: Business processes, not CRUD

4. Controllers/Resolvers (entry points)

   • Patterns: *Controller, *Resolver, API endpoints
   • Focus: Business capabilities, not technical routes

Phase 2: Group by Ubiquitous Language

For each concept, determine:

Primary Language Context

• What business vocabulary does this belong to?
• Examples:
  • Subscription, Invoice, Payment → Billing language
  • Movie, Video, Episode → Content language
  • User, Authentication → Identity language

Linguistic Boundaries

• Where do term meanings change?
• Same term, different meaning = different bounded context
• Example: "Customer" in Sales vs "Customer" in Support

Concept Relationships

• Which concepts naturally belong together?
• Which share business vocabulary?
• Which reference each other?

Phase 3: Identify Subdomains

A subdomain has:

• Distinct business capability
• Independent business value
• Unique vocabulary
• Multiple related entities working together
• Cohesive set of business operations

Common Domain Patterns:

• Billing/Subscription: Payments, invoices, plans
• Content/Catalog: Media, products, inventory
• Identity/Access: Users, authentication, authorization
• Analytics: Metrics, dashboards, insights
• Notifications: Messages, alerts, communications

Classify Each Subdomain:

Use this decision tree:

Is it a competitive advantage?  YES → Core Domain  NO → Does it require business-specific knowledge?        YES → Supporting Subdomain        NO → Generic Subdomain

Phase 4: Assess Cohesion

High Cohesion Indicators ✅

• Concepts share Ubiquitous Language
• Concepts frequently used together
• Direct business relationships
• Changes to one affect others in group
• Solve same business problem

Low Cohesion Indicators ❌

• Different business vocabularies mixed
• Concepts rarely used together
• No direct business relationship
• Changes don't affect others
• Solve different business problems

Cohesion Score Formula:

Score = (  Linguistic Cohesion (0-3) +    // Shared vocabulary  Usage Cohesion (0-3) +         // Used together  Data Cohesion (0-2) +          // Entity relationships  Change Cohesion (0-2)          // Change together) / 10
8-10: High Cohesion ✅5-7:  Medium Cohesion ⚠️0-4:  Low Cohesion ❌

Phase 5: Detect Low Cohesion Issues

Rule 1: Linguistic Mismatch

• Problem: Different business vocabularies mixed
• Example: User (identity) + Subscription (billing) in same service
• Action: Suggest separation into different bounded contexts

Rule 2: Cross-Domain Dependencies

• Problem: Tight coupling between domains
• Example: Service A directly instantiates entities from Domain B
• Action: Suggest interface-based integration

Rule 3: Mixed Responsibilities

• Problem: Single class handles multiple business concerns
• Example: Service handling both billing and content
• Action: Suggest splitting by subdomain

Rule 4: Generic in Core

• Problem: Generic functionality in core business logic
• Example: Email sending in billing service
• Action: Extract to Generic Subdomain

Rule 5: Unclear Boundaries

• Problem: Cannot determine which domain concept belongs to
• Example: Entity with relationships to multiple domains
• Action: Clarify boundaries, possibly split concept

Phase 6: Map Bounded Contexts

For each subdomain identified, suggest bounded context:

Bounded Context Characteristics:

• Name reflects Ubiquitous Language
• Contains complete domain model
• Has explicit integration points
• Clear linguistic boundary

Integration Patterns:

• Shared Kernel: Shared model between contexts (use sparingly)
• Customer/Supplier: Downstream depends on upstream
• Conformist: Downstream conforms to upstream
• Anti-corruption Layer: Translation layer between contexts
• Open Host Service: Published interface for integration
• Published Language: Well-documented integration protocol

Output Format

Domain Map

For each domain/subdomain:

## Domain: {Name}
**Type**: Core Domain | Supporting Subdomain | Generic Subdomain
**Ubiquitous Language**: {key business terms}
**Business Capability**: {what business problem it solves}
**Key Concepts**:
- {Concept} (Entity|Service|UseCase) - {brief description}
**Subdomains** (if applicable):
1. {Subdomain} (Core|Supporting|Generic)   - Concepts: {list}   - Cohesion: {score}/10   - Dependencies: → {other domains}
**Suggested Bounded Context**: {Name}Context
- Linguistic boundary: {where terms have specific meaning}- Integration: {how it should integrate with other contexts}
**Dependencies**:
- → {OtherDomain} via {interface/API}- ← {OtherDomain} via {interface/API}
**Cohesion Score**: {score}/10

Cohesion Matrix

## Cross-Domain Cohesion
| Domain A | Domain B | Cohesion | Issue              | Recommendation          || -------- | -------- | -------- | ------------------ | ----------------------- || Billing  | Identity | 2/10     | ❌ Direct coupling | Use interface           || Content  | Billing  | 6/10     | ⚠️ Usage tracking  | Event-based integration |

Low Cohesion Report

## Issues Detected
### Priority: High
**Issue**: {description}
- **Location**: {file/class/method}- **Problem**: {what's wrong}- **Concepts**: {involved concepts}- **Cohesion**: {score}/10- **Recommendation**: {suggested fix}
### Priority: Medium
{similar format}

Bounded Context Map

## Suggested Bounded Contexts
### {ContextName}Context
**Contains Subdomains**:
- {Subdomain1} (Core)- {Subdomain2} (Supporting)
**Ubiquitous Language**:
- Term: Definition in this context
**Integration Requirements**:
- Consumes from: {OtherContext} via {pattern}- Publishes to: {OtherContext} via {pattern}
**Implementation Notes**:
- Separate persistence- Independent deployment- Explicit API boundaries

Best Practices

Do's ✅

• Focus on business language, not code structure
• Let Ubiquitous Language guide boundaries
• Measure cohesion objectively
• Identify clear integration points
• Classify every subdomain (Core/Supporting/Generic)
• Look for linguistic boundaries first

Don'ts ❌

• Don't group by technical layers
• Don't force single global model
• Don't ignore linguistic differences
• Don't couple domains directly
• Don't create contexts by architecture
• Don't eliminate all dependencies (some are necessary)

Analysis Checklist

For Each Concept:

• What business language does it belong to?
• What domain/subdomain is it part of?
• Is it Core, Supporting, or Generic?
• What other concepts does it relate to?
• Are dependencies within same domain?
• Any linguistic mismatches?

For Each Domain:

• What is the Ubiquitous Language?
• What are the key concepts?
• What are the subdomains?
• Which is the Core Domain?
• What are cross-domain dependencies?
• Is internal cohesion high?
• Are boundaries clear?

For Cohesion Analysis:

• Calculate cohesion scores
• Identify low cohesion areas
• Map cross-domain dependencies
• Flag linguistic mismatches
• Note tight coupling
• Suggest boundary clarifications

Quick Reference

Subdomain Decision Tree

Analyze business capability└─ Is it competitive advantage?   ├─ YES → Core Domain   └─ NO → Is it business-specific?      ├─ YES → Supporting Subdomain      └─ NO → Generic Subdomain

Cohesion Quick Check

Same vocabulary? → High linguistic cohesionUsed together? → High usage cohesionDirect relationships? → High data cohesionChange together? → High change cohesion
All high → Strong subdomain candidateMix of high/low → Review boundariesAll low → Likely wrong grouping

Bounded Context Signals

Clear boundary signs:✅ Distinct Ubiquitous Language✅ Concepts have unambiguous meaning✅ Different meanings across contexts✅ Clear integration points
Unclear boundary signs:❌ Same terms with same meanings everywhere❌ Concepts used identically across system❌ No clear linguistic differences❌ Tight coupling everywhere

Anti-Patterns to Avoid

Big Ball of Mud

• Everything connected to everything
• No clear boundaries
• Mixed vocabularies
• Prevention: Explicit bounded contexts

All-Inclusive Model

• Single model for entire business
• Impossible global definitions
• Creates conflicts
• Prevention: Embrace multiple contexts

Mixed Linguistic Concepts

• Different vocabularies in same context
• Example: User/Permission with Forum/Post
• Prevention: Keep linguistic associations

Notes

• This is strategic analysis, not tactical implementation
• Focus on WHAT domains exist, not HOW to implement
• Some cross-domain dependencies are normal
• Low cohesion doesn't always mean "bad," it means "needs attention"
• Generic Subdomains naturally have lower cohesion
• Always validate with domain experts when possible

Validation Criteria

Good domain identification has:

• ✅ Clear boundaries with distinct Ubiquitous Language
• ✅ High internal cohesion within domains
• ✅ Explicit cross-domain dependencies
• ✅ Business alignment with capabilities
• ✅ Actionable recommendations for issues