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Item Assets Definition Specification

  • Title: Item Assets Definition
  • Identifier: item-assets
  • Field Name Prefix: -
  • Scope: Collection
  • Extension Maturity Classification: Proposal

A Collection extension to provide details about assets that are available in member Items.

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.

Collection fields

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, 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.

Field Name Type Description
item_assets Map<string, Asset Object> REQUIRED. A dictionary of assets that can be found in member Items

Asset Object

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.

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 syntax MAY be used for rich text representation.
type string Media type of the asset.
roles [string] The semantic roles of the asset, similar to the use of rel in links.

Other custom fields, or fields from other extensions may also be included in the Asset object.

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.

Implementations

  • AWS Public Dataset catalogs, landsat-8 and sentinel-2 define an Asset definition at the collection level.