Bounded Contexts

Bounded Contexts define explicit boundaries where a particular domain model applies, with its own ubiquitous language.

Core Idea

• Each context has clear boundaries
• Same term can mean different things in different contexts
• Each context has its own model
• Explicit translation at context boundaries

Examples

E-Commerce System

Sales Context:

// Customer in Sales context
public class Customer
{
    public CustomerId Id { get; }
    public string Name { get; }
    public Email Email { get; }
    public ShippingAddress PreferredAddress { get; }
    public List<Order> OrderHistory { get; }
}

Inventory Context:

// Customer in Inventory context (different model!)
public class Customer
{
    public CustomerId Id { get; }  // Same ID
    // Only what Inventory needs to know
    public bool IsVIP { get; }
    public int PriorityLevel { get; }
}

Shipping Context:

// Customer in Shipping context
public class Recipient  // Different name!
{
    public string Name { get; }
    public Address DeliveryAddress { get; }
    public PhoneNumber Contact { get; }
}

Context Boundaries

What Belongs in Same Context

• Shares same language
• Changes together
• Has consistent rules
• Single team ownership

What Belongs in Different Contexts

• Different language for same terms
• Independent change cycles
• Different business rules
• Different team ownership

Context Mapping

Shared Kernel

// Shared types between contexts
public class CustomerId  // Shared
{
    public Guid Value { get; }
}
 
public class Money  // Shared
{
    public decimal Amount { get; }
    public Currency Currency { get; }
}

Anti-Corruption Layer

// Translate from external context
public class LegacyOrderAdapter
{
    public Order ToModernOrder(LegacyOrderDto legacyOrder)
    {
        // Translate legacy model to our context's model
        return new Order(
            new OrderId(legacyOrder.order_id),
            new CustomerId(legacyOrder.cust_id),
            // ... translation logic
        );
    }
}

Benefits

• Prevents model confusion
• Team autonomy
• Independent evolution
• Clear integration points

Related Concepts

• Ubiquitous Language - Per-context language
• Microservices - Often align with bounded contexts
• Domain Driven Design - Overall pattern context

References