Applying Domain Driven Design - Model/Implementation

I'm quite new in the DDD-World and I'm just trying to figure out all the basics so please bear with me! I have the following Entities: - Datamodel - Object Types - Object Fields A datamodel can contain 1..* object types and each object type has a unique name and can contain 1..* object fields. A field has a certain type which is either string, int, date OR it is an relational type: type User { name: String age: Int articles: Article } type Article { name: String author: User } Now I have the folowing use cases: Add a object-type to the datamodel Remove a object-type from the datamodel Add the object-field to the object-type Remove the object-field from the content-type As far as I understood, all of my entities build the aggregate and the Datamodel entity is the root entity, is that correct? I came along with the following implementation approach: The Datamodel entity has the ability to add object-types and holds a list of object-types: public class Datamodel { private final List objectTypes = new ArrayList(); public void addObjectType(String name) { ObjectType objectType = new ObjectType(name); this.objectTypes.add(objectType); } } The Object-Type entity has the ability to add object-fields and holds a list of object-fields. public class ObjectType { private final String name; private final List fields = new ArrayList(); public ObjectType(String name) { this.name = name; } public void addField(Field field) { fields.add(Objects.requireNonNull(field)); } } If I now want to add a relational field to my object type, I need to ensure, that the datamodel contains an object type with the respective name, thus I need access to the list of object types within the datamodel entity. How would I model this scenario? Is that approach correct or should the Datamodel entity be responsible for adding both object-types and object-fields?

Feb 2, 2025 - 11:43

I'm quite new in the DDD-World and I'm just trying to figure out all the basics so please bear with me!

I have the following Entities: - Datamodel - Object Types - Object Fields

A datamodel can contain 1..* object types and each object type has a unique name and can contain 1..* object fields. A field has a certain type which is either string, int, date OR it is an relational type:

type User {
  name: String
  age: Int
  articles: Article
}

type Article {
  name: String
  author: User
}

Now I have the folowing use cases:

Add a object-type to the datamodel
Remove a object-type from the datamodel
Add the object-field to the object-type
Remove the object-field from the content-type

As far as I understood, all of my entities build the aggregate and the Datamodel entity is the root entity, is that correct?

I came along with the following implementation approach:

The Datamodel entity has the ability to add object-types and holds a list of object-types:

public class Datamodel {
    private final List objectTypes = new ArrayList<>();

    public void addObjectType(String name) {
        ObjectType objectType = new ObjectType(name);
        this.objectTypes.add(objectType);
    }
}

The Object-Type entity has the ability to add object-fields and holds a list of object-fields.

public class ObjectType {
  private final String name;
  private final List fields = new ArrayList<>();

  public ObjectType(String name) {
    this.name = name;
  }

  public void addField(Field field) {
    fields.add(Objects.requireNonNull(field));
  }
}

If I now want to add a relational field to my object type, I need to ensure, that the datamodel contains an object type with the respective name, thus I need access to the list of object types within the datamodel entity. How would I model this scenario?

Is that approach correct or should the Datamodel entity be responsible for adding both object-types and object-fields?