Merge pull request #1 from philvarner/label-role

use asset role instead of asset name to define which asset is the labels

CHANGELOG.md

@@ -6,6 +6,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+- assets should use role `labels` instead of an asset name of `labels`
+
 ## [1.0.2] - 2021-03-02
 ### Fixed
 - Updated schema self link

README.md

@@ -128,12 +128,16 @@ to be contained with a GeoJSON FeatureCollection:
 
 ### Assets
 
-#### labels (required)
-
-The Label Extension requires at least one asset that uses the key "labels".
-The asset will contain a link to the actual label data. The asset has these requirements:
-
-- is a GeoJSON FeatureCollection
+One or more assets will contain references to the label data. These assets have these requirements:
+
+- if the `label:type` is "vector", the labels must be a GeoJSON FeatureCollection.
+- if the `label:type` is "raster", it is recommended to also have an asset of a GeoJSON FeatureCollection 
+  defining the extent.
+- Asset Roles should be used to indicate which assets are the labels. It is recommended that all Assets 
+  referencing labels have the role `labels`.  Other labels such as `labels-vector` (for vector labels), 
+  `labels-raster` (for raster labels), `labels-extent` (for the vector extent of raster labels), `labels-training`
+   (for ML training data), and `labels-testing` (for ML testing data) may also be added to further indicate what 
+   specific assets reference.
 - if `label:tasks` is tile_classification, object_detection, or segmentation,
   each feature should have one or more properties containing the label(s) for the
   class (one of `label:classes`). the name of the property can be anything
@@ -142,6 +146,11 @@ The asset will contain a link to the actual label data. The asset has these requ
   defining the value for regression. the name of the property can be anything
   (use "label" if making from scratch), but needs to be specified in the `Item` with the `label:properties` field.
 
+#### Asset names
+
+The Label Extension recommends assets be named with the keys "raster_labels" or "vector_labels". However, 
+this is just a recommendation, and the names are entirely at the discretion of the implementer.
+
 #### Raster Label Notes
 
 If the labels are formatted as rasters - for example, a pixel mask with 1s