Which are common DDD (Domain-Driven Design) patterns?

Question

Specification pattern is a common pattern used in DDD that encapsulate business logic to respond to one question.

public interface ISpecification<T>
{
    bool IsSatisfiedBy(T aSource);
}

public class CustomerHaveDiscountSpec : ISpecification<Customer>
{
   bool IsSatisfiedBy(Customer aCustomer)
   {
       /* ... */
   }
}

Which other patterns are common in Domain-Driven Design?

Answer 1

I recommend InfoQ's Domain Driven Design Quickly, which does a good job of distilling the (too) longer book by Eric Evans. Building upon @Pangea's answer, the objects list deserves some description:

• Repository: encapsulates persistence and search - typically database
• Service: stateless API entity used for aggregate root CRUD
• Aggregate Root: an entity whose other child composite entities lack appropriate meaning without it - perhaps the most important aspect from an API perspective when talking about DDD
• Value Object: entity whose state does not change after instantiation (e.g. Color), particularly useful in multithreaded programming because using such eliminates concurrency issues