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UML diagrams

UMLMermaid.js

UML Diagrams in Documentation

Unified Modeling Language (UML) is a standardized way to visualize system architecture. Using diagrams helps stakeholders and developers understand complex logic quickly without having to read hundreds of lines of text.

All diagrams below are built using Mermaid.js — a Markdown-based diagramming tool that integrates directly into documentation.

Basic01 / Flowchart

Flowchart — Basic Level

A fundamental example showing a logical execution path or decision-making process. Each node has a specific shape — diamonds for conditions, rectangles for actions. It is the perfect tool for describing business logic and process flows.

Click to see the detailed explanation of the Basic Flowchart

Diagram Overview

This flowchart illustrates a standard decision-making process during a development cycle. It uses standard UML shapes: Rectangles for actions/processes and a Diamond for a decision point.

The Logic Flow

  1. Start — The process begins at the entry point.
  2. Decision Point (Is there an error?) — The system checks for the presence of bugs or configuration issues. This acts as a logical gate that determines the next step based on a boolean (Yes/No) result.
  3. Branch A (Yes → Fix the code) — If an error is detected, the flow moves to the remediation phase. After the fix, the logic loops back to the decision point to re-verify.
  4. Branch B (No → Deploy project) — If no errors are found, the system proceeds to the deployment phase.
  5. End — The process successfully terminates after deployment is complete.

Diagram

Intermediate02 / Sequence Diagram

Sequence Diagram — Intermediate Level

Illustrates how objects or services interact with each other over time. It displays the exchange of messages between different participants in the system. The vertical lines represent time moving from top to bottom.

Click to see the detailed explanation of the Authentication Sequence

Participants

  • User — The human actor interacting with the application's interface.
  • Browser — The frontend (client-side) application that handles the UI and user input.
  • Server API — The backend (server-side) system that manages data, logic, and authentication.

The Step-by-Step Process

  1. User Input (Enters credentials) — The process begins when the User interacts with the login form. The Browser captures this input.
  2. Request Initiation (POST /login request) — The Browser packages the credentials into a secure HTTP POST request and sends it to the /login endpoint on the Server API.
  3. Server-Side Processing & Validation — The Server API validates the credentials. If authenticated, it generates a JWT (JSON Web Token) as a session key.
  4. Response (200 OK (JWT Token)) — The Server API sends back an HTTP 200 OK response containing the JWT Token.
  5. Navigation (Redirect to Dashboard) — The Browser stores the token and triggers a client-side redirect, moving the User to the Dashboard.

Diagram

Advanced03 / State Diagram

State Diagram — Advanced Level

Used to describe the behavior of complex systems that change their state based on specific events. This scheme is indispensable for technical API documentation or order management systems where tracking transitions between statuses is critical.

Click to see the detailed explanation of the State Diagram

Diagram Overview

This state diagram represents the lifecycle of a background task or a process worker. Unlike a flowchart which shows a path, a state diagram shows the different states a system can be in and the events that trigger transitions between them.

State Transitions and Logic

  1. Initial State (Solid Circle) — The entry point indicating where the system life cycle begins.
  2. Idle — The default state where the system is waiting for input. It is "listening" for a trigger.
  3. Transition (New task received) — An external event occurs that pushes the system out of the Idle state.
  4. Processing — The active state where the core logic or computation is being executed.
  5. Conditional Outcomes:
    • Success Branch (Task completed) — If the work finishes correctly, the system moves to the Success state and then reaches the Final State (double circle).
    • Error Branch (Execution failed) — If something goes wrong, the system transitions to the Error state.
  6. Retry Logic — From the Error state, the system follows the "Retry logic" path back to Processing to attempt the task again.

Diagram

Expert04 / State Machine

The Hyper-Complex State Machine

This model represents a resilient, distributed system capable of handling unexpected failures and edge cases. It incorporates high-availability patterns such as circuit breakers, backoff strategies, and hierarchical idle states.

Technical Specification: Advanced State Transition Logic & Fault Tolerance

Architectural Overview

This Finite-State Machine formalizes a resilient worker lifecycle. It moves beyond simple success/failure paths to incorporate high-availability patterns such as resource orchestration and circuit breakers, ensuring state integrity even during infrastructure instability.

1. Pre-Execution & Quiescence

  • Initialization & Bootstrapping — Upon instantiation, the system executes a self-diagnostic. A FatalError at this stage triggers an immediate shutdown to prevent corrupted execution.
  • Hierarchical Idle State — The system operates in a multi-stage waiting mode, encompassing Active Polling, Data Fetching, and Payload Validation. This ensures the core execution state is never reached with malformed data.

2. Execution & Resource Orchestration

  • Processing Micro-states — The execution phase is governed by a ResourceCheck loop. This prevents process hanging during CPU or memory exhaustion by transitioning to a Paused state until the environment stabilizes.
  • State Persistence — Before final evaluation, the system enters an Evaluating state to verify that the output meets all business logic constraints.

3. Fault Tolerance & Exception Handling

The system distinguishes between three types of failure to optimize recovery:

  • Transient Failures — Handled via a Backoff & Retry strategy, allowing for recovery from temporary network blips or database locks.
  • Timeouts — Monitored via a dedicated latency recorder to identify performance bottlenecks in the infrastructure.
  • Circuit Breaker Logic — If the error threshold is breached, the system "trips" the breaker, locking the state to prevent "retry storms" and transitioning to Manual Intervention for audit.

4. Deterministic Termination

  • Post-Process Cleanup — Upon reaching Success, the system executes a cleanup routine to de-allocate resources before entering the terminal sink.
  • Finality Guards — This model ensures that no process is left in a "zombie" state; every path leads to either a clean disposal or an audited manual reset.

Diagram

Expert05 / Class Diagram

Docusaurus Homepage

A React-based Docusaurus homepage represented via a Component Architecture Diagram (Class Diagram style). This visualizes how the different functional components relate to each other and the data they handle.

Technical Specification: Architectural Explanation

  • The Root (Home) — This is your entry point that orchestrates the overall layout of the landing page.

  • Encapsulation — The logic for fetching external data is isolated within TomJohnsonLatestPost. This is a clean design because the rest of the homepage doesn't need to know about the RSS feed logic.

  • Asynchronous Flow — The diagram shows the dependency on RSS_API, representing the useEffect hook in your code that triggers the side effect of network communication.

Architecture tip

Class diagrams excel at showing component hierarchies and data dependencies. Use them alongside sequence diagrams to cover both static structure and runtime behavior.

Diagram

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