🧠 Domain-Driven Design (DDD) means modeling systems using the language of the business. It requires tight collaboration between developers and domain experts so the software directly reflects how the business operates.

🧭 Strategic vs Tactical Design Tools

DDD talks about two kinds of design tools:

• Strategic Design Tools
• Tactical Design Tools

🧠 Strategic Design

Strategic design maps how different parts of the domain connect and where boundaries should be drawn.

It involves:

• Defining bounded contexts
• Identifying subdomains
• Establishing the relationships between different contexts

Key Concepts:

• Bounded Contexts
• Ubiquitous Language
• Context Mapping

🧩 Tactical Design

Tactical design dives into the details of each bounded context and defines the internal building blocks of the system.

It applies DDD patterns such as:

• Entity
• Aggregate
• Value Object
• Domain Event
• Repository
• Factory

🔑 Key Concepts of Domain-Driven Design

📌 Domain

The subject area that the software is intended to address.
Example — E-Commerce system

📌 Subdomain

A part of the domain that can be isolated and worked on separately.
Example — ProductManagement, OrderManagement, CustomerManagement

📌 Bounded Context

A boundary within which a particular model is defined and applicable.
Example:

• Product Management Context — Adding, updating, removing products
• Order Management Context — Creating/updating orders

📌 Ubiquitous Language

A common language used by both developers and domain experts.
Example — Product, Cart, Order, Customer

📌 Context Mapping

Identifies relationships and interactions between bounded contexts.
Example — Product and Order Context collaboration for stock validation

🧱 Tactical Building Blocks

🧍 Entity

An object with a unique identity and lifecycle.
Example — Customer

🏗️ Aggregate

A cluster of domain objects treated as a single unit.
Example — Order with many OrderLineItems

🧾 Value Object

Represents a descriptive aspect with no identity.
Example — Address, Money

📢 Domain Event

A record of a significant change in the domain.
Example — OrderPlacedEvent, ProductAddedToCartEvent

🗃️ Repository

Stores, retrieves, and manages domain objects.
Example — ProductRepository, OrderRepository

🏭 Factory

Encapsulates object creation logic.
Example — OrderFactory builds order aggregates from cart

✅ Benefits of Domain-Driven Design

• Improved Communication: Ubiquitous language bridges devs and domain experts
• Focus on Core Complexities: Helps build a more maintainable system

⚠️ Challenges of Domain-Driven Design

• Complexity: Especially in large, evolving domains
• Overkill for Simple Domains: Not always suitable for straightforward business logic