migrate spec from stac-spec repo (#1)

* migrate spec from stac-spec repo

* add PR template

* fix package template reference; remove rc.1 suffix

* fix references to core stac in schema

* update schema text

* update schema

Author: Phil Varner

.github/pull_request_template.md

@@ -0,0 +1,13 @@
+**Related Issue(s):** #
+
+
+**Proposed Changes:**
+
+1. 
+2. 
+
+**PR Checklist:**
+
+- [ ] This PR is made against the `dev` branch (all proposed changes except releases should be against `dev`, not main).
+- [ ] This PR has **no** breaking changes.
+- [ ] I have added my changes to the CHANGELOG **or** a CHANGELOG entry is not required.

.remarkignore

@@ -0,0 +1 @@
+/CHANGELOG.md

CHANGELOG.md

@@ -6,6 +6,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+- Added clarification about how collection-level asset object properties do 
+  not remove the need for item-level asset object properties in the `item-assets` extension ([#880](https://github.com/radiantearth/stac-spec/pull/880))
+
 ### Added
 
 ### Changed
@@ -17,3 +20,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 [Unreleased]: <https://github.com/stac-extensions/template/compare/v1.0.0...HEAD>
+
+## [v1.0.0-beta.1] - 2020-05-29
+
+### Changed
+
+- `asset` extension renamed to `item-assets` and renamed `assets` field in Collections to `item_assets`
+- `item-assets` extension only requires any two fields to be available, not the two specific fields `title` and `type`

README.md

@@ -1,50 +1,67 @@
-# Template Extension Specification
+# Item Assets Extension Specification
 
-- **Title:** Template
-- **Identifier:** <https://stac-extensions.github.io/template/v1.0.0/schema.json>
-- **Field Name Prefix:** template
-- **Scope:** Item, Collection
+- **Title:** Item Assets
+- **Identifier:** <https://stac-extensions.github.io/item-assets/v1.0.0/schema.json>
+- **Field Name Prefix:** n/a
+- **Scope:** Collection
 - **Extension [Maturity Classification](https://github.com/radiantearth/stac-spec/tree/master/extensions/README.md#extension-maturity):** Proposal
-- **Owner**: @your-gh-handles @person2
+- **Owner**: @matthewhanson
 
-This document explains the Template Extension to the [SpatioTemporal Asset Catalog](https://github.com/radiantearth/stac-spec) (STAC) specification.
-This is the place to add a short introduction.
+This document explains the Item Assets Extension to the 
+[SpatioTemporal Asset Catalog](https://github.com/radiantearth/stac-spec) (STAC) specification.
+
+This extension serves two purposes:
+
+1. Provide a human-readable definition of assets available in any Items 
+  belonging to this Collection so that the user can determine the key(s) 
+  of assets they are interested in.
+2. Provide a way to programmatically determine what assets are available 
+   in any member Item. Otherwise a random Item needs to be examined to 
+   determine assets available, but a random Item may not be representative of the set.
 
 - Examples:
-  - [Item example](examples/item.json): Shows the basic usage of the extension in a STAC Item
-  - [Collection example](examples/collection.json): Shows the basic usage of the extension in a STAC Collection
+  - [Landsat-8 Collection Example](examples/example-landsat8.json): Shows the basic usage of the extension in a STAC Collection
 - [JSON Schema](json-schema/schema.json)
 - [Changelog](./CHANGELOG.md)
 
-## Item Properties and Collection Fields
+## Collection Fields
 
-| Field Name           | Type                      | Description |
-| -------------------- | ------------------------- | ----------- |
-| template:new_field   | string                    | **REQUIRED**. Describe the required field... |
-| template:xyz         | [XYZ Object](#xyz-object) | Describe the field... |
-| template:another_one | \[number]                 | Describe the field... |
+This extension introduces a single new field, `item_assets` at the top level of a Collection.
+An Asset Object defined at the Collection level is nearly the same as the 
+[Asset Object in Items](https://github.com/radiantearth/stac-spec/tree/v1.0.0-rc.1/item-spec/item-spec.md#asset-object), except for two differences.
+The `href` field is not required, because Collections don't point to any data by themselves, but at least two other fields must be present.
 
-### Additional Field Information
+| Field Name  | Type                                       | Description |
+| ----------- | ------------------------------------------ | ----------- |
+| item_assets | Map<string, [Asset Object](#asset-object)> | **REQUIRED.** A dictionary of assets that can be found in member Items |
 
-#### template:new_field
+### Asset Object
 
-This is a much more detailed description of the field `template:new_field`...
+An asset is an object that contains details about the datafiles that will be included in member Items.
+Assets included at the Collection level do not imply that all assets are available from all Items.
+However, it is recommended that the Asset Definition is a complete set of all assets that may be available from any member Items.
 
-### XYZ Object
+| Field Name  | Type      | Description |
+| ----------- | --------- | ----------- |
+| title       | string    | The displayed title for clients and users. |
+| description | string    | A description of the Asset providing additional details, such as how it was processed or created. [CommonMark 0.29](http://commonmark.org/) syntax MAY be used for rich text representation. |
+| type        | string    | [Media type](https://github.com/radiantearth/stac-spec/tree/v1.0.0-rc.1/catalog-spec/catalog-spec.md#media-types) of the asset. |
+| roles       | \[string] | The [semantic roles](https://github.com/radiantearth/stac-spec/tree/v1.0.0-rc.1/item-spec/item-spec.md#asset-role-types) of the asset, similar to the use of `rel` in links. |
 
-This is the introduction for the purpose and the content of the XYZ Object...
+Other custom fields, or fields from other extensions may also be included in the Asset object.
 
-| Field Name  | Type   | Description |
-| ----------- | ------ | ----------- |
-| x           | number | **REQUIRED**. Describe the required field... |
-| y           | number | **REQUIRED**. Describe the required field... |
-| z           | number | **REQUIRED**. Describe the required field... |
+Any property that exists for a Collection-level asset object must also exist in the corresponding assets object in 
+each Item. If a collection's asset object contains properties that are not explicitly stated in the Item's asset 
+object then that property does not apply to the item's asset. Item asset objects at the Collection-level can 
+describe any of the properties of an asset, but those assets properties and values must also reside in the item's 
+asset object. To consolidate item-level asset object properties in an API setting, consider storing the STAC Item 
+objects without the larger properties internally as 'invalid' STAC items, and merge in the desired properties at 
+serving time from the Collection-level.
 
-## Relation types
+At least two fields (e.g. `title` and `type`) are required to be provided, in order for it to adequately describe Item assets.
+The two fields must not necessarily be taken from the list above and may include any custom field.
 
-The following types should be used as applicable `rel` types in the
-[Link Object](https://github.com/radiantearth/stac-spec/tree/master/item-spec/item-spec.md#link-object).
+## Implementations
 
-| Type                | Description |
-| ------------------- | ----------- |
-| fancy-rel-type      | This link points to a fancy resource. |
+- AWS Public Dataset catalogs, [landsat-8](http://landsat-stac.s3.amazonaws.com/landsat-8-l1/catalog.json) 
+- and [sentinel-2](http://sentinel-stac.s3.amazonaws.com/sentinel-2-l1c/catalog.json) define an Asset definition at the Collection level.