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Structural Modeling ​

Structural models represent the static structure of a system. They show the components of the system and the relationships between them, without concern for their dynamic, time-based behavior. These diagrams are like architectural blueprints. They are essential for designing the architecture, understanding its components, and communicating the design to developers.

Class Diagrams ​

Class diagrams are the main building block of any object-oriented solution. They describe the structure of a system by showing the system's classes, their attributes, operations (or methods), and the relationships between objects.

Key Relationships ​

  • Association: A general relationship between classes (--).
  • Aggregation: A "has-a" relationship, where one class contains another, but the contained class can exist independently (o--).
  • Composition: A strong "has-a" relationship, where the contained class cannot exist without the container (*--).
  • Inheritance (Generalization): An "is-a" relationship, where one class inherits from another (<|--).

Example: University System ​

This diagram models classes for a university, showing relationships between Department, Professor, and Student.

Advanced Example: Payment Processing System ​

This class diagram illustrates a simplified payment processing system, showcasing inheritance, composition, and interface implementation.

Component Diagrams ​

Component diagrams are used to visualize the physical components of a system, such as libraries, files, and executables, and the relationships (dependencies) between them. They provide a high-level view of the system's architecture from a module or component perspective.

Key Components ​

  • Component: A modular part of the system, represented by a rectangle with a component icon.
  • Provided Interface: An interface that a component exposes to other components.
  • Required Interface: An interface that a component needs from another component.
  • Dependency: A relationship showing that one component depends on another.

Example: Web Application Architecture ​

This diagram shows the high-level components of a typical web application.

Advanced Example: Microservices E-commerce System ​

This diagram illustrates a microservice-based e-commerce platform, highlighting interactions between different services and their dependencies.

Entity-Relationship Diagrams (ERDs) ​

Entity-Relationship Diagrams (ERDs) are used to model the structure of a database. They show the entities (tables), their attributes (columns), and the relationships between them.

Mermaid.js provides a specific syntax for creating ERDs that is clear and easy to read.

Key Relationships ​

  • One-to-One: ||--||
  • One-to-Many: ||--|{
  • Many-to-Many: }|--|{ (often resolved with a linking table)
  • Identifying vs. Non-identifying: A solid line for identifying relationships (the child's key depends on the parent's) and a dashed line for non-identifying relationships.

Example: Blogging Platform Database ​

This ERD models the database for a simple blog with users, posts, and comments.

Advanced Example: Social Media Platform ​

This ERD models a more complex social media platform with users, posts, comments, likes, and followers, including many-to-many relationships and self-referencing tables.