Demystifying UML: Models, Diagrams, and Views in Software Design

  • Posted on September 12, 2023
  • /Under UML
Table of Contents hide
1 Distinguishing Between Models, Diagrams, and Views in UML
2 Some Examples
3 Diagram vs View vs Model in UML
4 Summary

Distinguishing Between Models, Diagrams, and Views in UML

In UML (Unified Modeling Language), “diagram,” “view,” and “model” are related concepts that play different roles in modeling and representing various aspects of a system. Let’s clarify each of these terms:

  1. Model:
    • A model in UML represents an abstract, conceptual description of a system or a part of a system. It serves as the foundation for understanding and communicating the system’s structure, behavior, and interactions.
    • A UML model can encompass a wide range of information, including class definitions, relationships, use cases, state machines, sequence diagrams, and more.
    • A model is typically independent of any specific notation or graphical representation. It can be documented using textual descriptions, diagrams, or a combination of both.
  2. Diagram:
    • A diagram in UML is a graphical representation of a specific aspect or view of a UML model. Diagrams are used to visualize and communicate different aspects of a system.
    • There are several types of UML diagrams, each designed to represent specific information and relationships within the model. Examples include class diagrams, use case diagrams, sequence diagrams, and state machine diagrams.
    • Diagrams provide a visual way to understand and communicate various aspects of the model, making it easier for stakeholders to grasp the system’s architecture, behavior, and structure.
  3. View:
    • A view in UML refers to a specific perspective or subset of a UML model that focuses on a particular aspect or concern of the system.
    • Views are used to simplify complex models by breaking them down into more manageable pieces, each of which addresses a specific aspect, such as structural, behavioral, or deployment views.
    • Views help different stakeholders, such as developers, architects, and business analysts, focus on the parts of the model that are relevant to their roles and concerns. For example, a software architect may primarily work with structural views (e.g., class diagrams), while a business analyst may focus on use case diagrams to understand system functionality.

Some Examples

Let’s use a simple example related to a library management system to illustrate these concepts in UML.

Model:

  • The UML model for a library management system includes all the essential information and representations of the system. It encompasses a wide range of details, such as classes, relationships, use cases, and interactions.
  • For instance, it defines classes like Book, Library, Member, and their associations, as well as use cases like Borrow Book and Return Book. It also includes behavior descriptions and constraints.

Diagram:

  • A diagram is a graphical representation of a specific aspect of the model. Let’s consider a class diagram as an example:
    • Class Diagram: This diagram represents the structural aspect of the library management system. It shows classes, their attributes, and relationships. For instance:
      • It visually depicts the Book class with attributes like title, author, and ISBN.
      • It illustrates associations between Member and Library classes, indicating that members are associated with a library.
      • It may also show multiplicity (e.g., one library can have many books).

View:

  • A view represents a particular perspective of the model, focusing on a specific concern or aspect. For instance:
    • Structural View: This view could include the class diagram, emphasizing the static structure of the library management system.
    • Behavioral View: Another view might contain a sequence diagram that shows how a member borrows a book, emphasizing the dynamic behavior of the system.
    • Deployment View: A third view may consist of a deployment diagram illustrating how the software components are distributed across physical nodes (servers), addressing deployment concerns.

In this library management system example, the model encompasses all the information about the system. The diagrams provide graphical representations of specific aspects, such as structure or behavior. Views help stakeholders focus on the relevant parts of the model based on their roles and concerns, whether they are concerned with the system’s structure, behavior, or deployment.

Diagram vs View vs Model in UML

Aspect Model Diagram View
Definition Abstract, conceptual representation Graphical representation Subset or perspective of the model
Scope Encompasses the entire system Focuses on specific aspect Focuses on specific concern or view
Contents Various elements (e.g., classes, use cases, interactions) Graphical elements (e.g., shapes, lines, notations) Specific subset of elements, views, or diagrams
Purpose Foundation for understanding and communicating system details Visualize and communicate specific aspects Simplify and tailor information for stakeholders
Examples – Class definitions – Class diagram for structural view – Structural view (class diagram) for architects
– Use cases and scenarios – Sequence diagram for behavioral view – Behavioral view (sequence diagram) for developers
– Interaction diagrams – Deployment diagram for deployment view – Deployment view (deployment diagram) for system administrators

This table highlights the distinctions between “Model,” “Diagram,” and “View” in UML, focusing on their definitions, scope, contents, purposes, and examples

Summary

a UML model represents the abstract, conceptual description of a system, and it can be documented using diagrams and textual descriptions. Diagrams are graphical representations of specific aspects of the model and are used to visualize and communicate that information. Views are subsets or perspectives of the model that focus on specific concerns, allowing stakeholders to work with relevant portions of the model without being overwhelmed by its complexity. Together, these concepts help in modeling, documenting, and communicating complex systems effectively.

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