fix: comments from PR review

Author: gadomski

README.md

@@ -79,18 +79,26 @@ This default is so that the entity returned is a valid STAC Item.
 Implementations may choose to include other properties, e.g., `properties.created`, but the number
 of default properties attributes should be kept to a minimum.
 2. If only `include` is specified, these attributes should be the only attributes included.
-3. If only `exclude` is specified, these attributes should be subtracted from the full item.
-This may result in an entity that is not a valid STAC Item.
+If additional fields are provided beyond those in the `include` list, the number and size of
+these attributes should be kept to a minimum.
+3. If only `exclude` is specified, these attributes fields should not be
+included in the response Item object, but every other fields available for the
+Item should be included.`
 4. If `exclude` is specified and `include` is null or an empty
 array, then the `exclude` attributes should be excluded from the default set.
-This may result in an entity that is not a valid STAC Item.
-5. If a key is in `exclude`, and a sub-key is in `include`, the sub-key should be included, but no other fields
-in the key should be included.  For example, if `properties` is excluded and `properties.datetime` is included, then `datetime`
-should be the only attribute in `properties`.
-6. If a key is in `include`, and a sub-key is in `exclude`, the key should be included, and the sub-key should be excluded.
-For example, if `properties` is included and `properties.datetime` is excluded, then `datetime`
-should not be in `properties`.
-7. If the same attribute is present in both `include` and `exclude`, it should be included.
+5. For nested attributes (e.g. `properites.datetime`), the most specific path
+should be honored first, and `include` should be preferred over `exclude`. For
+example:
+    1. If a field is in `exclude`, and a nested attribute of that field is in
+    `include`, the nested attribute should be included, but no other nested
+    attributes in the field should be included.  For example, if `properties` is
+    excluded and `properties.datetime` is included, then `datetime`
+    should be the only nested attribute in `properties`.
+    2. If a field is in `include`, and a nested attribute is in `exclude`, the field
+    should be included, and the nested attribute should be excluded.  For example,
+    if `properties` is included and `properties.datetime` is excluded, then
+    `datetime` should not be in `properties`.
+6. If the same field is present in both `include` and `exclude`, it should be included.
 
 ## Examples
 
@@ -138,7 +146,7 @@ JSON
 }
 ```
 
-Exclude `geometry` from the full item.  This **must** return an entity that is not a valid GeoJSON Feature or a valid STAC Item.
+Exclude `geometry` from the full item.  This will return an entity that is not a valid GeoJSON Feature or a valid STAC Item.
 
 Query Parameters
 
@@ -159,7 +167,9 @@ JSON
 ```
 
 Return the `id`, `type`, `geometry`, and the Properties attribute `eo:cloud_cover`.
-This might not return a valid STAC Item, since not all required Item attributes are included.
+This is not guaranteed not return a valid STAC Item, since not all required Item
+attributes are included, but an implementor may choose to return a valid STAC
+item anyways.
 
 Query Parameters