There are several technologies you should learn about if your going to understand how HAX is built (and how to extend it)

JSON Schema

Learn more about JSON Schema on the official website for that standard. JSON Schema provides a way of describing the data contained in a JSON blob so that a form can be built to modify those values. HAX uses this extensively via a tag called eco-json-schema-object and related tags, to turn any json schema definition into a fully two-way data binded form.

Example

HAX schema is an abstraction that sits on top of JSON Schema in order to provide forms for updating values in your HAX wired elements. If you wanted to extend the types of input fields that HAX has access to then learning JSON Schema would be the best place to start!

JSON Outline Schema

JSON Outline Schema is a standard way of expressing and storing the relation between objects. It gives you a simple way of linking data together to form an outline of related concepts / entities. Here is an example of a JSON Outline schema entity:

This gives you enough data to visually represent this information in an outline form. Let's look at a larger example of 3 items related together which would express nested hierarchy in a consistent way:

Let's break down these properties and why we have them in the schema:

Higher order schema

Leaf / page element within the structure