Domain Driven Design

Domain-Driven Design (DDD)

Core Concepts

DDD is a software engineering approach that centers the design around the business domain, bridging the gap between technical and business teams.

1. Ubiquitous Language

A strict, shared vocabulary used by both domain experts (business) and developers. If the business calls it a "Guest", the code should not call it a "User".

2. Bounded Contexts

Large systems have overlapping models. A "Product" in the Inventory context means weight and dimensions. A "Product" in the Sales context means price and marketing description. Bounded contexts isolate these models so they don't corrupt each other.

3. Aggregates & Roots

An Aggregate is a cluster of domain objects treated as a single unit. The Aggregate Root is the only object external entities can reference. (e.g., An Order is the root; OrderLineItem cannot be accessed directly).

DDD Architecture Map

%%{init: {"theme": "default", "flowchart": {"useMaxWidth": true}}}%%
flowchart TD
    subgraph ECommerce ["E-Commerce Domain"]
        
        subgraph SalesContext ["Sales Bounded Context"]
            A["Order (Aggregate Root)"]
            B["OrderLineItem (Entity)"]
            A --- B
        end
        
        subgraph InventoryContext ["Inventory Bounded Context"]
            C["Product (Aggregate Root)"]
            D["WarehouseLocation (Value Object)"]
            C --- D
        end
        
    end
    
    subgraph AntiCorruption ["Anti-Corruption Layer (ACL)"]
        E["Event Translator"]
    end
    
    A -.->|"OrderPlacedEvent"| E
    E -.->|"Translate to Inventory terms"| C