Domain Modeling - Software Engineering

Domain modeling is an important step in software engineering. It means making a simple picture or description of the real world and things that the system will work with. This helps everyone understand and plan how the system should work before actually building . It is understood as abstract modeling. A site model could be an illustration of the ideas or objects shown within the drawback domain. It additionally captures the apparent relationships among these objects. Samples of such abstract objects area unit the Book, Book Register, member register, Library Member, etc.

The objects known throughout domain analysis are classified into 3 types:

• Boundary objects
• Controller objects
• Entity objects

The boundary and controller objects are consistently known from the employment case diagram whereas the identification of entity objects needs to apply. So, the crux of the domain modeling activity is to spot the entity models.

The purpose of various sorts of objects known throughout domain analysis and the way these objects move among one another.

The different styles of objects known throughout domain analysis and the area of their relationship unit as follows:

Boundary Objects

Boundary Objects are the parts of a system that directly interact with users, such as screens, menus, forms, and dialogs. They are responsible primarily for user input and output, including validating inputs and formatting displayed information. Boundary objects do not contain business or process logic but serve as the gateway through which users communicate with the system. Typically, one boundary object is designed for each actor or use case to maintain clear interaction boundaries. Their main goal is to facilitate smooth and effective user interaction without managing core data or processes as below says:

• Handle user interaction
• Validate and format inputs/outputs
• No business logic
• One per actor/use case

Controller Objects

Controller Objects act as the coordinators between boundary and entity objects, managing the flow and business logic required to fulfill a use case. They encapsulate the operational logic that may change over time and ensure the system’s components work together seamlessly. Controllers decouple the interface (boundary) from the data (entity) layers, making the system more flexible and easier to maintain. Usually, one controller corresponds to one use case, but complex scenarios may require multiple controllers or multiple states within a single controller to manage various aspects of the process. They usually:

• Manage business logic and workflows
• Coordinate boundary and entity objects
• Decouple UI and data layers
• One controller per use case, or multiple for complex cases

Entity Objects

Entity Objects represent the core data and information that the system manages and stores persistently, such as records or business entities like books, members, or registers. These objects encapsulate the stored data and provide basic operations to retrieve or update it. Entity objects are often “dumb servers,” meaning they perform minimal processing or logic beyond data storage and retrieval. They exist beyond the lifespan of any single use case execution and model real world or conceptual information within the system. They actually :

• Store persistent data
• Represent real world/business entities
• Provide basic data operations
• Minimal logic, mostly data handling

Steps to Create a Domain Model

• Learn About the Domain: Work closely with experts to gain a clear understanding of the business or problem area.
• Identify Main Concepts: Determine the important entities and objects that play a role in the domain.
• Specify Attributes and Connections: Define the characteristics of each entity and how they relate to one another.
• Create the Model Diagram: Use tools like UML class diagrams to visually represent the domain structure.
• Review with Stakeholders: Confirm that the model accurately reflects real world needs and expectations.

Advantages of Domain Modeling

• Better Understanding
  Helps both developers and stakeholders understand real world entities and their relationships.
• Improves Communication
  Makes it easier for team members and clients to talk and agree on what the system should do. It acts as a shared language between business analysts, developers, and clients.
• Helps Design the System
  Gives a clear structure to build the software the right way from the beginning.
• Easier to Update
  If something changes, it's easier to update the system when the model is clear.
• Reuses Ideas
  Good models allows you to reuse parts of the system in other places.
• Removes Confusion
  Makes the rules and logic of the system clear and consistent.
• Fits Well with Agile
  Works well with step-by-step (agile) development by focusing on the important parts first.

Disadvantages of Domain Modeling

• Time Consuming
  To create an accurate and detailed domain model takes significant time and effort, especially in complex domains.
• Requires Domain Expertise
  If there is no input from domain experts, the model may be inaccurate or incomplete.
• Can Be Over Engineered
  There is risk of creating unnecessarily complex models that don't add real value to the project.
• Difficult to Adapt for Rapid Changes
  In this fast changing environments, constantly updating the domain model can slow down development.
• Initial Learning Curve
  For the new teams, learning how to use domain-driven design or UML (Unified Modeling Language) can be difficult to understand at first.

Example: Query Book Availability Use Case in a Library Information System (LIS)

Consider the use case “query book availability” in a Library Information System. This use case simply involves checking if a given book name matches any books listed in the catalog. In this simple scenario, only one controller object is needed to handle the process. For example, a complex use case might involve controllers like a group action manager, resource scheduler, and error handler working together.

There are also situations where a single use case involves multiple controller objects. Often, use cases require the controller to move through several states during execution. In such cases, it may be necessary to create a separate controller object for each instance or execution of the use case to manage these states properly.