harmony/docs/guides/developer-guide.md

Developer Guide

This section covers how to extend Harmony by building your own Score, Topology, and Capability implementations.

Writing a Score

A Score is a declarative description of desired state. To create your own:

1. Define a struct that represents your desired state
2. Implement the Score<T> trait, where T is your target Topology
3. Implement the Interpret<T> trait to define how the Score translates to infrastructure actions

See the Writing a Score guide for a step-by-step walkthrough.

Writing a Topology

A Topology models your infrastructure environment. To create your own:

1. Define a struct that holds your infrastructure configuration
2. Implement the Topology trait
3. Implement the Capability traits your Score needs

See the Writing a Topology guide for details.

Adding Capabilities

Capabilities are the specific APIs or features a Topology exposes. They are the bridge between Scores and the actual infrastructure.

See the Adding Capabilities guide for details on implementing and exposing Capabilities.

Core Traits Reference

Trait	Purpose
Score<T>	Declares desired state ("what")
Topology	Represents infrastructure ("where")
Interpret<T>	Execution logic ("how")
Capability	A feature exposed by a Topology

See Core Concepts for the conceptual foundation.