Simplifications and Clarifications #2, add example + JSON schema

README.md

@@ -4,7 +4,6 @@
 - **Identifier:**
   - <https://stac-extensions.github.io/ceos-ard/v0.2.0/schema.json>
   - See section [Profiles](#profiles) for more
-
 - **Field Name Prefix:** ceos_ard
 - **Scope:** Item, Collection
 - **Extension [Maturity Classification](https://github.com/radiantearth/stac-spec/tree/master/extensions/README.md#extension-maturity):** Proposal
@@ -19,7 +18,7 @@ which itself is planned to be deprecated. **WORK IN PROGRESS**
 - Examples:
   - [Item example](examples/item.json): Shows the basic usage of the extension in a STAC Item (ToDo)
   - [Collection example](examples/collection.json): Shows the basic usage of the extension in a STAC Collection (ToDo)
-- [JSON Schema](json-schema/schema.json) (ToDo)
+- [JSON Schema](json-schema/schema.json)
 - [Changelog](./CHANGELOG.md) (ToDo)
 
 ## Fields
@@ -32,6 +31,9 @@ The fields in the table below can be used in these parts of STAC documents:
 - [ ] Assets (for both Collections and Items, incl. Item Asset Definitions in Collections)
 - [ ] Links
 
+The fields don't need to be provided in each Item to minimize the required changes in the Items.
+The fields can be provided in the Items to make the fields available in search.
+
 | Field Name                     | Data Type | Description |
 | ------------------------------ | --------- | ----------- |
 | ceos_ard:type                  | string    | **REQUIRED.** The CEOS-ARD (sensor) type implemented, one of `optical` or `radar`. |