The Blue Book of UX Directives

Preface

This book establishes a doctrine of Human-Centered Systems Engineering for the design, governance, and evolution of digital systems.

How to read this book: This is written as a field manual, not an essay—terse, absolute, and command-form by design. The register is deliberate: it is the doctrine language of the U.S. Army, where I served, carried into the discipline of human-centered systems.

• “Directives are written to be met, not debated.”
• “A standard you can defer is not a standard.”

The purpose of the book is to codify enforceable standards that can be consistently applied, tested, and upheld across teams and systems—serving, for now, as a scaffold for best practices rather than a showcase of their practical application, which is reserved for future work.

This edition serves three functions:

1. Defines non-negotiable, human-centered principles that must guide digital system behavior.
2. Provides operational directives for translating those principles into product requirements and engineering decisions.
3. Creates a shared organizational framework for evaluating, auditing, and evolving UX and AI-mediated systems.

“Those who are in love with practice without knowledge are like the sailor who gets into a ship without rudder or compass and who never can be certain whither he is going. Practice must always be founded on sound theory.”

Leonardo da Vinci. From “The Notebooks of Leonardo Da Vinci”. I. Prolegomena and General Introduction to the Book on Painting (between 1480 and 1519).

How this book is organized

Two parts: Chapters 1–8 codify principles that hold for any interactive system. They are arranged as layers of the interaction—the human, information, action, system behavior, visual form, coherence, trust, and evolution over time. A concept is governed in the earliest layer where it arises and referenced from later ones.

Chapter 9 stands apart by design. It governs systems whose behavior is probabilistic or changes through learning—systems that can be wrong in ways no fixed rule predicts. These principles are still forming and have not yet settled into industry standards, so they are kept separate rather than folded into the general chapters. Where a chapter 9 directive specializes a general one, the general directive still applies.

Outcomes, laws, and practices: Most subcategories govern a property of the system. A few govern something else and are placed where they apply: 1.7 Simplicity is the outcome of chapter 1; 3.5 User Efficiency is the goal of chapter 3, and 3.6 Fitts’s Law is the physical law it obeys; 6.4 Design System Integrity, 8.3 Observability, and 8.4 Validation are practices of the team that builds the system.

Repealed directives: A directive that duplicated another keeps its ID, is marked Repealed, and points to the directive that replaces it. IDs are never reused.

General provisions

These provisions apply to every chapter. Directives that restate them locally are their applications.

1. Proportionality. The strength of every safeguard, signal, and explanation scales with the consequence of the action it governs.
2. Automation rigor. The more a system acts on its own, the stronger its oversight, explanation, and validation must be.
3. Confirm only the irreversible. Reversibility replaces confirmation; explicit confirmation is reserved for actions that cannot be undone.
4. Automation is offered, not imposed. Automation that reduces effort must remain optional and subordinate to user intent.