Atom

The Atom Syndication Format, standardized as RFC 4287, is an XML-based web feed format for publishing lists of content — blog posts, news, updates — in a machine-readable way. It was created to be a more rigorously and openly specified alternative to the several competing versions of RSS, and it is paired with the Atom Publishing Protocol (RFC 5023) for creating and editing web resources over HTTP. Together they were an early, influential answer to the question of how machines should read and write syndicated content.

• XML feed format - Entries and feed metadata follow a precise, namespaced schema that parsers can rely on.
• RFC-standardized - Being defined in an IETF RFC gave Atom the unambiguous specification RSS lacked.
• Atom Publishing Protocol - A companion HTTP-based protocol for creating and editing entries, an early model for REST-style content APIs.
• Discoverable - Feeds are advertised via link elements so clients and crawlers find them automatically.

In real operations, Atom remains a quiet workhorse: plenty of blogs, changelogs, and status pages still expose an Atom feed that tools poll for updates, and its publishing protocol prefigured the resource-oriented design later formalized in REST and OpenAPI. For an API provider, a well-formed Atom or RSS feed on a blog or changelog is one of the cheapest machine-readable signals you can ship — and increasingly a way for agents to keep current on what a platform is changing without scraping a web page.