Additional Identifiers Extension Specification

• Title: Additional Identifiers
• Identifier: https://stac-extensions.github.io/external-ids/v1.0.0/schema.json
• Field Name Prefix: -
• Scope: Item, Collection, Catalog
• Extension Maturity Classification: Proposal
• Owner: @m-mohr

This document explains the Additional Identifiers Extension to the SpatioTemporal Asset Catalog (STAC) specification, also known as "externalIds" in OGC API - Records.

This extension offers a way to expose additional, external identifiers (IDs) in STAC, which is an additive mechanism to the id field in STAC.

All specifications originate from externalIds as defined in OGC API - Records.

• Examples:
  • STAC Item
  • STAC Collection
• JSON Schema
• Changelog

Fields

The fields in the table below can be used in these parts of STAC documents:

• Catalogs
• Collections
• Item Properties (excl. Summaries in Collections)
• Assets (for both Collections and Items, incl. Item Asset Definitions in Collections)
• Links

Field Name	Type	Description
externalIds	[External ID Object]	REQUIRED. A list of additional identifiers for the resource.

Note: externalIds should not be summarized in Collection Summaries due to its individual nature for each Item.

External ID Object

Field Name	Type	Description
value	string	REQUIRED. The value of the identifier.
scheme	string	A reference to an authority or identifier for a knowledge organization system from which the external identifier was obtained. It is recommended that the identifier be a resolvable URI.

Contributing

All contributions are subject to the STAC Specification Code of Conduct. For contributions, please follow the STAC specification contributing guide Instructions for running tests are copied here for convenience.

Running tests

The same checks that run as checks on PR's are part of the repository and can be run locally to verify that changes are valid. To run tests locally, you'll need npm, which is a standard part of any node.js installation.

First you'll need to install everything with npm once. Just navigate to the root of this repository and on your command line run:

npm install

Then to check markdown formatting and test the examples against the JSON schema, you can run:

npm test

This will spit out the same texts that you see online, and you can then go and fix your markdown or examples.

If the tests reveal formatting problems with the examples, you can fix them with:

npm run format-examples