CF Extension Specification

• Title: CF
• Identifier: https://stac-extensions.github.io/cf/v0.2.0/schema.json
• Field Name Prefix: cf
• Scope: Item, Collection
• Extension Maturity Classification: Proposal
• Owner: @Fred-Leclercq

This document explains the CF Extension to the SpatioTemporal Asset Catalog (STAC) specification. It adds a field to provide the Standard Name Table based on the CF metadata convention.

• Examples:
  • Item and Collection: Shows the basic usage of the extension in a STAC Item and a corresponding summarizing STAC Collection
  • Standalone Collection: Shows the basic usage of the extension in a STAC Collection without items
• 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
cf:parameter	[CF Object]	REQUIRED. CF Standard Name Table

Additional Field Information

cf:parameter

The cf:parameter array is used to describe the parameters in an Asset or Collection. It requires at least one entry with a non-empty name. This enables clients to read the file and understand which parameters are available.

If assets with a cf:parameter array are provided, the field may optionally be used in the Item Properties or Collection and it must summarize the available parameters in the assets. This must be the 'union' of all the possible parameters represented in assets. If no assets are provided in a Collection, the field can be used freely to describe the Collection for e.g. search. An Item is only allowed to use cf:parameter in its Properties if it has at least one asset with a defined parameter array.

The cf:parameter list in Item Properties or Collections should be considered merely informative - clients should rely on the cf:parameter of each asset, if available.

CF Object

This object should contain a variable name from the CF list and where applicable a unit from the UDUNITS-2 database

Field Name	Type	Description
name	string	REQUIRED. Should be a non-empty value from the CF standard names list
unit	string	Indicates the unit, preferably available in the database from the UDUNITS-2 package (unidata)

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