Spec-Driven Development: Who Executes a Spec? (Part 4 of 4)

This is the fourth and final part of a series defining spec-driven development (SDD). After breaking down the concept in previous parts, it's time to put everything together and examine the bigger picture. A spec in this context has specific characteristics in terms of format, language, content, and lifecycle. Different specifications employ various levels of abstraction and guide the development process. The critical question remains: who is actually executing the spec?

Throughout the discussion, the focus has been on the artifacts and procedures involved in SDD, but the human actors have been largely unaddressed. The chain from intent to execution could be fully autonomous with AI agents, semi-autonomous with human involvement at every step, or fully manual. The core of SDD, as I view it, is the autonomous translation of the spec and design into source code by AI coding agents.

However, manual modifications are still allowed and encouraged as long as they remain within the bounds of the spec and don't introduce new behaviors.

The level of human involvement in SDD can be defined on a spectrum, ranging from fully manual to fully autonomous. Regardless of the level of human involvement, validation of the deliverable against the spec is crucial. The spec should be testable, and its conformance should be validated to ensure the final product meets its intended requirements.

Ultimately, the definition of SDD hinges on three core principles:

1. A spec dictates the testable behavior of the deliverable, not the how or why.

2. The spec must exist continuously and drive the development process until the end of life.

3. The translation of the spec to source code must be performed autonomously by AI coding agents, with manual modifications allowed provided they adhere to the spec.

As the tech industry grapples with the nuances of SDD, it's essential to remember that the devil is in the details. To make SDD a success, we must consistently provide detailed specifications to avoid ambiguity and ensure the development process runs smoothly.