Themes Extension Specification

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

This document explains the Themes Extension to the SpatioTemporal Asset Catalog (STAC) specification. This extension is meant to support knowledge organization systems used to classify the resource (i.e. controlled vocabularies / keywords such as Geonames or Wikipedia). If you just need "uncontrolled" free-form keywords / tags, please use the keywords field instead. This extension is based on the field themes as defined in OGC API - Records.

• Examples:
  • Item example: Shows the basic usage of the extension in a STAC Item
  • Collection example: Shows the basic usage of the extension in a 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 (incl. Summaries in Collections)
• Assets (for both Collections and Items, incl. Item Asset Definitions in Collections)
• Links

Field Name	Type	Description
themes	[Theme Object]	REQUIRED. A knowledge organization system used to classify the STAC entity. Each element is a concept and their respective knowledge organization system / controlled vocabulary.

Theme Object

The Theme Object aims at defining a normalized list of concepts based on a knowledge organization system / controlled vocabulary (e.g. geonames).

Field Name	Type	Description
concepts	[Concept Object]	REQUIRED. One or more entity/concept identifers from this knowledge system.
scheme	string	REQUIRED. An identifier for the knowledge organization system used. It is recommended that the identifier is a resolvable URI.

Concept Object

Describes an individual concept from the knowledge system.

Field Name	Type	Description
id	string	REQUIRED. An identifier for the concept.
title	string	A human readable title for the concept.
description	string	A human readable description for the concept.
url	string	RECOMMENDED. A URI providing further description of the concept.

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