Instruction file imported from BVSSHA-MSE/SSHA (.github/instructions/ddd/ddd-core-philosophy.instructions.md). Copyright stays with the author.

DDD Core Philosophy

When designing or reviewing DDD code, apply these core principles

Phase: 🔨 implement

Domain First

Model the business domain, not the database or framework

# ❌ WRONG: Database Framework driven naming
class EFOrderContainers
  attr_accessor :order_status_id, :fk_customer
end

# ✅ CORRECT: Domain-driven naming
class Order
  attr_reader :status, :customer
end

Ubiquitous Language

Use the same terms domain experts use—in code, docs, and conversation

# ❌ WRONG: Technical jargon
def process_entity(dto)

# ✅ CORRECT: Business language
def place_order(cart)

Bounded Contexts

Explicitly define where each model/term is valid. Same word can mean different things in different contexts

# ✅ Billing context: Customer has payment methods
module Billing
  class Customer
    attr_reader :payment_methods
  end
end

# ✅ Shipping context: Customer has addresses
module Shipping
  class Customer
    attr_reader :shipping_addresses
  end
end

Continuous Learning

• Refine models as understanding deepens
• Expect naming and structure to evolve
• Collaborate with domain experts regularly

Iterative Refinement

• Evolve code and language together
• Refactor toward deeper insight, not just cleaner code
• When domain expert language changes, update code to match