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An activity diagram to describe the resolution of HTTP response status codes, given various headers, implemented via semantical callbacks.

This is part of a bigger effort Forget HTTP.

And it goes on Twitter as #httpdd - HTTP Decision Diagram.

This is a follow-up/fork of Alan Dean's http-headers-status.

Why, why, why

Why is this helpful?

Watch Webmachine: Focus on Resources - Sean Cribbs from Øredev Conference on Vimeo.

Sean also has a good rundown of why an FSM is a good match for a protocol specification/implementation.


This repository's goal is to build on previous work, and set a "reference" in terms of a HTTP decision diagram and necessary callbacks.

In doing so, we take a snapshot of the current Webmachine callbacks that are linked to Alan Dean's http-headers-status, and trying to do constructive criticism and addressing outstanding issues

  • in a v4 diagram
  • by adding/modifying Webmachine's callbacks
  • with clear definitions of the steps/logic implied by the callbacks
  • with a diagram described as FSM thanks to Cosmogol, with a JSON AST export.

Take it also as a process of gaining context, while the existing callbacks and the existing diagram may be spot on.

Kudos to



Apache 2.0