Feed

A feed is a sequence of entities that chronicle modifications to a resource, organized into multiple pages. Each page contains at least one or more entities.

Typically, a page in a feed includes three Link HTTP headers:

• self: the URL of the current page
• prev: the URL of the preceding page
• next: the URL of the subsequent page

NOTE: The initial page lacks a prev link, and the final page omits a next link. Additional details on this can be found in RFC 8288.

Refer to Page Format for the structure of each page, which accommodates one or more entities.

Required headers

There are some required headers for every page. For a feed page, the Link; rel=next and Link; rel=prev header is optional.

Finding an entry point

Each feed consumer needs to find a valid starting point. This can be determined reading the feed from the beginning or by using a snapshot as a starting point. The snapshot’s creation date serves as the entry point.

Pagination

To ensure efficient navigation and access for feed consumers, it’s essential for providers to incorporate pagination mechanisms. This process involves crawling to the feed through both HEAD requests and GET requests for retrieving specific pages. Think about a doubly-linked list of pages, where each page has a prev and next link.

NOTE: Links must be consistent, i.e. the prev and next links of adjacent pages must match and the feed must not form a loop.

Last-Modified

Each entity must have a Last-Modified header. They must be formatted using the timestamp format for HTTP Last-Modified Headers.

NOTE: The must be monotonically increasing across all pages.

Immutability of pages

Treat published pages as immutable once created, with a few specific exceptions:

• New entities can be added to the most recent page if it doesn’t have a next link.
• A next link can be introduced to the most recent page, after which it becomes immutable.
• A prev link may be removed from an older page as part of a gradual cleanup process.