Add Deep Traversal & Routing section to README

README.md

@@ -1,10 +1,13 @@
 # STAC API - Children Extension Specification <!-- omit in toc -->
 
-- [Overview](#overview)
-- [Link Relations](#link-relations)
-- [Endpoints](#endpoints)
-- [Pagination](#pagination)
-- [Example](#example)
+
+- [STAC API - Children Extension Specification](#stac-api---children-extension-specification)
+  - [Overview](#overview)
+  - [Link Relations](#link-relations)
+  - [Endpoints](#endpoints)
+  - [Pagination](#pagination)
+  - [Deep Traversal & Routing](#deep-traversal--routing)
+  - [Example](#example)
 
 ## Overview
 
@@ -70,6 +73,23 @@ the [STAC - Features Collection Pagination section](https://github.com/radiantea
 To the greatest extent possible, the catalog should be structured such that all children can be
 retrieved from the endpoint in a single call.
 
+## Deep Traversal & Routing
+
+While the primary endpoint is defined at the API Root (`/children`), this extension pattern MAY be applied to any Catalog or Collection resource within the API to enable deep, recursive traversal (similar to a file system).
+
+To inspect the children of a specific sub-resource, clients should append `/children` to the resource's canonical URI.
+
+**Examples:**
+* **Root Children:** `GET /children`
+* **Sub-Catalog Children:** `GET /catalogs/{id}/children`
+* **Collection Children:** `GET /collections/{id}/children` (for "Collection of Collections" hierarchies)
+
+### Filtering by Type
+Because the `children` array is polymorphic (containing both `Catalog` and `Collection` objects), implementations SHOULD support a `type` query parameter to allow clients to request a specific resource type.
+
+* `GET /children?type=Catalog`
+* `GET /children?type=Collection`
+
 ## Example
 
 Below is a minimal example, but captures the essence. Each object in the `children` array