Publications · Apress Book · Free Guide

The book &
the guide

Spec-driven development, from the source.
Two publications by Simon Martinelli, creator of the AI Unified Process (AIUP). Spec-Driven Development, the Apress pocket guide, walks the whole lifecycle from requirements to executable code. Writing Use Cases for AI goes deep on the specification format at its heart, and it is free.
The Book · Apress Pocket Guides

Spec-Driven Development #

From Specs to Code with AI Agents. Specifications as the single source of truth.

Book cover: Spec-Driven Development: From Specs to Code with AI Agents by Simon Martinelli

Traditional development is code-centric: specifications are written after the fact, if at all, and drift out of date the moment the code changes. The result is maintenance pain, stalled modernization, and systems that no longer match what the business needs. AI coding tools generate code faster, but they don't fix this underlying process problem.

Spec-Driven Development flips the model around. Specifications become the single source of truth that drives code, tests, and validation. The book introduces the AI Unified Process, a lightweight framework that makes spec-driven development practical with today's AI agents, and shows how emerging tools like Amazon Kiro and GitHub Spec Kit fit into the picture.

A hands-on case study runs through the whole book, taking you from requirements to executable code so you can see every step of the lifecycle in action, not just read about it.

Written for software developers, tech leads, and architects. Basic programming knowledge is all you need; no prior requirements engineering or AI tool experience is required.

Inside

What you'll learn #

Capture Requirements in Lightweight Specs

Write specifications that are precise enough for AI agents yet light enough for real projects: living artifacts, not throwaway prompts.

Treat Specs as Executable Contracts

Use specifications to drive code generation and testing, so the system's behavior is defined once and enforced everywhere.

Apply the AI Unified Process

Bring the methodology to your own projects and team workflows, including iterations, roles, and artifacts.

Integrate AI Agents into the Lifecycle

Put AI agents to work across the spec-driven lifecycle: generating, regenerating, and refactoring code, tests, and documentation.

Chapter by Chapter

Table of contents #

Ten chapters from the why to the how, including a complete case study.

  1. 01 Why Spec-Driven Development?
  2. 02 The AI Unified Process in a Nutshell
  3. 03 From Requirements to Specs
  4. 04 Writing Executable Specifications
  5. 05 Specs Driving Code in Practice
  6. 06 Specs As Tests
  7. 07 Tools for Spec-Driven Development
  8. 08 Case Study: Building a Simple Task Manager
  9. 09 Scaling Spec-Driven Development
  10. 10 Best Practices, Pitfalls, and the Road Ahead
Details

Book facts #

Publisher & Series

Apress, part of the Apress Pocket Guides series. Compact, practical, and focused.

Publication Date

August 2026. Available now in softcover and eBook formats.

ISBN

Softcover: 979-8-8688-2850-8
eBook: 979-8-8688-2851-5

Scope

152 pages with 23 illustrations, including a complete hands-on case study from requirements to executable code.

The Author

About Simon Martinelli #

Simon Martinelli is a Java Champion, Vaadin Champion, and Oracle ACE Pro with more than 30 years of experience as a software architect, developer, consultant, and trainer. He is the creator of the AI Unified Process and the founder of Martinelli LLC, where he coaches teams in AI-driven development. He also lectures at two Swiss universities on software architecture, DevOps, and cloud-native development.

The Free Guide · Leanpub

Writing Use Cases for AI #

A free companion guide: how to write use cases for stakeholders, engineers, and AI agents.

Guide cover: Writing Use Cases for AI: How to write use cases for stakeholders, engineers, and AI agents by Simon Martinelli

Writing the code is no longer the expensive part. Expressing intent precisely is. The use case is where that intent gets written down, and it now has three readers at once: the stakeholder who validates it, the engineer who reviews the implementation against it, and the AI agent that generates code from it. This guide shows how to write one specification that serves all three.

It builds on what you already know from Cockburn or Use-Case 3.0 instead of repeating it, and concentrates on what actually changes when an AI agent reads your use case: how precise to be, what to deliberately leave out, where use cases sit in the artifact chain of the AI Unified Process, and how they drive slices, tests, change requests, and brownfield work.

Eleven chapters with a complete specification template, a worked example, patterns for scenarios and alternative flows, checklists, and the mistakes that show up most often in review.

The guide is free. Leanpub lets you set your own price, and $0 is fine. You get PDF, EPUB, and in-browser reading, DRM-free and with free updates for as long as the guide is maintained.

Get your copy

Get the publications #

The book is available now in softcover and eBook formats; the guide Writing Use Cases for AI is free. Want to go deeper? Workshops and consulting bring the AI Unified Process directly to your team.