Modeling the Domain

Adding a Diagram

You can add Diagrams to your Domain Package. By default, Application Templates typically include a default one. Diagrams are useful for:

  • Visualizing your domain.
  • Visually modeling your domain.
  • Visualizing subsets or logical areas of a large domain.
  1. Right-click on the Domain package and select New Diagram.
  2. If the designer was in Tree-view, it will switch to a diagram view.
  3. Rename the diagram by right-clicking it in the Tree-view and selecting Rename.
  4. Add domain elements to your diagram:
    • From the context menu, select Add to Diagram and choose Elements to add to the Diagram.
    • Drag domain elements, like Classs, from the Tree-view onto the diagram.
    • Model new domain elements.
  5. Optionally, create multiple diagrams for different perspectives. The Tree-view remains the source of truth.
Tip

Hold down CTRL while dragging elements from the Tree-view to include directly associated elements.

Diagram View

Creating an Entity

An Entity is a core building block in domain modeling that represents a uniquely identifiable object within a system, such as a Customer or Order. Entities are essential because they encapsulate business rules and behavior, ensuring the system consistently reflects the real-world concepts they model.

Note

While we typically do domain modeling in diagrams, it's important to realize that the Tree-view is the source of truth. Diagrams are simply a visualization of the domain or a part of the domain.

  1. Add an Entity to the diagram.
  2. Give your Entity a name.
Note

The Entity's element type is Class.

You can now model various aspects of your entity:

  • Attributes: Model the data of your Entity.
  • Associations: Model the relationships between your Entitys.
  • Constructors: Model the construction of your Entity.
  • Operations: Model the behavior of your Entity.

Capturing Attributes

To model the data of an Entity:

  1. Add Attribute (Ctrl + Shift + A) on a class.
  2. Enter the name of the Attribute.
  3. Press Tab and select the Type for the attribute.
Tip

Pressing F2 on an attribute allows you to rename and change its type.

Tip

If you have an Attribute selected, pressing CTRL+ENTER will add a new Attribute to the class and begin editing it. This is very useful for rapidly capturing attributes.

Capturing Constructors

To model constructors of an Entity:

  1. Add Constructor (Ctrl + Shift + U) on a class.
  2. Capture any parameters as required.

Capturing Operations

To model operations (mnethods) of an Entity:

  1. Add Operation (Ctrl + Shift + O) on a class.
  2. Enter the name of the Operation.
  3. Press Tab and select the Return Type for the operation.
  4. Capture any parameters as required.

Capturing parameters for constructors and operations

To model parameters for a constructor or an operation on a class:

  1. Add Parameter (Ctrl + Shift + A) on a class.
  2. Enter the name of the Parameter.
  3. Press Tab and select the Type for the parameter.
Tip

Pressing F2 on an parameter allows you to rename and change its type.

Tip

If you have an Parameter selected, pressing CTRL+ENTER will add a new Parameter and begin editing it. This is very useful for rapidly capturing parameters.

Adding Entity Associations

To model the relationships an Entity has with other Entitys:

  1. Ensure both Entitys are on the diagram; use Add to Diagram if needed.
  2. Right-click on the Entity that will own the relationship, hover your mouse over New Association, and select the type of relationship you want from the submenu (e.g., Many to One).
  3. Left-click on the related Entity to create the association between them.
Note

For more details on modeling domain Associations, click here.

Basic Domain

Inheritance with Entities

To inherit one Entity from another:

  1. Right-click on the Entity that will inherit and select New Inheritance.
  2. Select the parent Entity.

Inheritance Entity

Creating a Domain Contract

A Domain Contract encapsulates a specific intent or operation to be performed within a domain, bundling the data required for that operation into a single object. They help maintain clear and explicit boundaries in the domain, promoting separation of concerns and ensuring the domain logic operates on well-defined inputs. Domain Data Contracts are sometimes referred to as (domain) Data Transfer Objects or Command Objects.

Note

The Domain Contract's element type is Data Contract.

  1. Add Domain Contract in the Tree-view.
  2. Name your Domain Contract.
  3. Right-click the Domain Contract and select Add Attribute to define its data.
  4. Add complex data types as needed:
    • Domain Contract for modeling nested structures.
    • Enum for modeling enumerations.

Domain Contract

Modeling Entity Associations

Entity Associations are modeled using a UML style visualization, and define the relationships between Entitys.

Domain Association

Visually the Associations communicates the following:

-Multiplicity, the numbers above the Association indicate the multiplicity, 1 to Many (1 -*) in the example above. -Ownership, denoted by the diamond shape, its colour indicates the type of ownership. -Navigability, arrows on the line show navigability from one entity to another, Order will have a OrderItems property.

Multiplicity

When adding an association you can use the sub-menu to choose the multiplicity you want e.g. 1 to Many, 1 to 1 etc. You can adjust the multiplicity, in the Properties pane by changing the Is Nullable and Is Collection properties on the Association Ends (Source End and Target End).

Multiplicity for an Association End is configured as follows:

Multiplicity IsNullable IsCollection
1 ⬜ ⬜
0..1 ✅ ⬜
* ⬜ ✅

Ownership

When creating an Association the Entity you create it from will be the owner, you can see this visually by the diamond on the Association line attached to the owning Entity.

There are two types of ownership which can be modeled and this ownership is inferred by the multiplicity. These ownership types are Composition (black diamond) and Aggregation (white diamond).

Composition relationship

  1. When attempting to represent real-world whole-part relationships, e.g. an engine is a part of a car.
  2. When the container is destroyed, the contents are also destroyed, e.g. a university and its departments.

- Wikipedia

Tip

An entity should never have multiple Composition relationships pointint to different owners, this is a logical modeling error as an Entity can only have 1 owner.

Aggregation relationship

  1. When representing a software or database relationship, e.g. car model engine ENG01 is part of a car model CM01, as the engine, ENG01, may be also part of a different car model.[8]
  2. When the container is destroyed, the contents are usually not destroyed, e.g. a professor has students; when the professor dies the students do not die along with them.

- Wikipedia

Relationship Ownership Type
0..1 -> 0..1 white diamond
0..1 -> 1 white diamond
0..1 -> * white diamond
1 -> 0..1 black diamond
1 -> 1 black diamond
1 -> * black diamond
* -> 0..1 white diamond
* -> 1 white diamond
* -> * white diamond
Tip

You can convert a black diamond relationship to a white diamond by changing the owner of the relationship, i.e. create the relationship from the other Entity.

By default Navigability is configured to be from Owner to target Entity. If you want bi-directional navigation, simply check Navigable on the Source End of the association in the Properties pane.

Modeling Entity associations can be a bit of an art who "owns" a relationship can be subjective and should be driven by your use cases.

Modeling Multiple Domains with Different Persistence Concerns

You can model and connect your application to multiple domains by adding additional Domain Packages in the Domain Designer.

To create multiple domains:

  1. Create a New Domain Package

    • In the Domain Designer, right-click in the tree view and select New Package.
    • Alternatively, use the Create New Package button in the toolbar.

    New Domain Package

  2. Name the Domain Package

    • Provide a meaningful name for the Domain Package.

    New Domain Package Name

  3. Define the Database Type

    • Apply the appropriate stereotype to specify the type of database the domain will use.
    • Available options depend on the installed modules.

    Domain Type

    Tip

    The available database type options are determined by the installed modules. For example, to use the Document Database stereotype, a corresponding implementation modules like Intent.MongoDb or Intent.CosmosDB must be installed. Similarly, for the Relational Database stereotype, a module such as Intent.EntityFrameworkCore must be installed.

  4. Configure Database Settings

    • Set any required settings for the selected database type.

    Database Provider

    Tip

    If a single implementation module (e.g. Intent.MongoDb or Intent.CosmosDB for example) is installed, it will automatically be used as the default provider, eliminating the need to set it explicitly.

Each domain can now be modeled separately in their own respective package as per the instructions detailed in this page.