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7. Collection Metadata Best Practices#
7.1 Overview#
This chapter presents the requirements and recommendations that apply to STAC collection metadata representations (returned by a static or searchable catalog, in isolation or included in a search response) in addition to the general metadata requirements presented in Metadata Best Practices.
The requirements and recommendations provided relate to:
Properties
Asset and roles
Links and relations
Facilitating federation
7.2 Properties#
CEOS-STAC-REQ-7210 - Collection representation [Requirement]
A(n EO) Collection metadata record shall be represented as a STAC Collection according to version v1.0.0 of the “STAC Collection Specification” [AD02].
The above requirement is added as the title is optional in the STAC Collection specification.
CEOS-STAC-REC-7215 - Collection metadata dates [Recommendation]
A(n EO) Collection metadata record should encode metadata dates using the
$.created,$.updatedand$.publishedproperties according to the “STAC Timestamps Extension Specification” [AD20].
{
"stac_version": "1.0.0",
"stac_extensions": [
"https://stac-extensions.github.io/timestamps/v1.1.0/schema.json" ],
"id": "Radarsat-2",
"type": "Collection",
"title": "RADARSAT-2 ESA Archive",
"created": "2020-10-26T00:00:00.000Z",
"updated": "2023-11-10T08:04:18Z",
"published": "2020-11-01T00:00:00.000Z"
}
CEOS-STAC-REQ-7220 - Platform information [Requirement]
A(n EO) Collection metadata record shall encode the platform name(s) as
$.summaries.platformproperty and use the platform name corresponding to the GCMD platforms preferred label.
CEOS-STAC-REQ-7230 - Instrument information [Requirement]
A(n EO) Collection metadata record shall encode the instrument name(s) as
$.summaries.instrumentsproperty and use the instrument names corresponding to the GCMD instruments preferred label.
CEOS-STAC-REQ-7240 - Science keywords [Requirement]
A(n EO) Collection metadata record shall encode related science keywords as
$.keywordsproperty and use the science keywords corresponding to the GCMD Earth Science) preferred label.
"keywords": [
"EARTH SCIENCE>AGRICULTURE",
"EARTH SCIENCE>BIOSPHERE>ECOSYSTEMS>TERRESTRIAL ECOSYSTEMS>FORESTS",
"EARTH SCIENCE>LAND SURFACE",
"EARTH SCIENCE>BIOSPHERE>VEGETATION" ],
"summaries": {
"instruments": [
"AVNIR-2",
"SLIM6",
"MSC"
],
"platform": [
"ALOS-1",
"GEOSAT-1",
"KOMPSAT-2"
]
}
CEOS-STAC-REQ-7250 - DOI [Requirement]
The DOI of a collection, if available, shall be encoded according to the Scientific Citation Extension Specification, i.e. using the
$.sci:doiproperty and a link object with rel=”cite-as” [AD13].
For additional guidance about use of persistent identifiers (e.g. DOI), refer to the “CEOS WGISS Persistent Best Practice” [RD06].
A(n EO) Collection metadata record shall encode provider information as $.providers[*] and use the GCMD Providers preferred label (skos:prefLabel) as $.providers[*].name.
"id": "TropForest",
"stac_extensions": [
"https://stac-extensions.github.io/scientific/v1.0.0/schema.json",
],
"providers": [
{
"roles": [
"producer"
],
"name": "ESA/ESRIN",
"url": "https://esa.int"
}
],
"sci:doi": "10.5270/esa-qoe849q",
"links": [
{
"rel": "cite-as",
"href": "https://doi.org/10.5270/esa-qoe849q",
"type": "text/html",
"title": "Landing page"
}
]
If there is a need to advertise the provider email address then an email property should be added in the Provider Object.
"providers": [
{
"roles": [
"producer"
],
"name": "ESA/ESRIN",
"url": "https://esa.int",
"email": "eohelp@esa.int"
}
]
7.3 Assets and roles#
CEOS-STAC-REQ-7310 - Item assets [Recommendation]
In the case where all granules of a collection contain the same asset types, these assets should be provided in the collection encoding as
Item assetas defined in the “STAC Item Assets Definition Extension Specification” [AD25].
The example below indicates that all granules of this collection do have assets, representing a thumbnail of type PNG, a download location as .zip file and are also available as zarr, with an alternative download location on S3 object storage. Note that the keys used for the assets (e.g. “thumbnail”, “enclosure”, “data”) are meaningless and can have any value.
"item-assets": {
"thumbnail": {
"roles": [
"thumbnail"
],
"type": "image/png",
"title": "THUMBNAIL"
},
"enclosure": {
"roles": [
"data"
],
"type": "application/zip",
"title": "Download"
},
"data": {
"title": "Zarr consolidated metadata",
"type": "application/json"
"roles": [
"data",
"metadata",
"zarr-consolidated-metadata"
],
"alternate": {
"s3": {
"title": "S3 Access"
}
}
}
}
7.4 Links and relations#
CEOS-STAC-REC-7420 - Support for granule search [Recommendation]
Collections supporting granule search should contain a link with rel=”http://www.opengis.net/def/rel/ogc/1.0/queryables” and type=”application/schema+json” in the STAC collection representation.
CEOS-STAC-REQ-7430 - Support for granule search [Requirement]
STAC Granule Catalogs shall advertise all “additional” collection specific search/filter parameters applicable for a granule search within a collection in the corresponding queryables object for that collection and not rely on a global set of queryables applicable to all collections made available via a link with rel=”http://www.opengis.net/def/rel/ogc/1.0/queryables” from the landing page (typically “/collections/{collectionId}/queryables” instead of “/queryables”), to be combined with a collection-specific set (which may be empty).
CEOS-STAC-REC-7450 - Reference to license [Recommendation]
CEOS STAC collection metadata should include a Link object with rel=”license” to reference an external file describing the license information for the collection, unless the
licenseproperty has a specific SPDX license identifier.
7.5 Facilitating catalog federation#
This is required to allow federation into CEOS IDN which has a similar requirement for collection metadata provided in DIF-10 format.
7.6 CEOS-ARD#
CEOS-ARD [AD30] publishes Product Family Specifications (PFS) that define recommendations and requirements to make certain types of data available as Analysis-Ready Data (ARD).
The CEOS-ARD specifications are available as specification text and it doesn’t provide an official mapping to STAC. A community-lead project aims at providing a mapping between the CEOS-ARD requirements and existing STAC extensions, which can be used as a guideline for STAC implementations that aim for CEOS-ARD compliance. See the STAC CEOS-ARD Extension Specification [AD28] and its Optical and Radar profiles for details.