HTML REMAINS THE MOST POPULAR HYPERMEDIA FORMAT IN USE TODAY, but as the Web extends its reach beyond the browser, we’re seeing other useful formats emerge. Of these newer hypermedia types, one in particular deserves our attention: the Atom Syndication Format, or Atom for short. Atom is an XML-based hypermedia format for representing timestamped lists of web content and metadata such as blog postings and news articles.
In Chapter 5, we used a custom hypermedia format to expose data and protocols to consumers. By contrast, Atom is a general-purpose hypermedia format.
Atom interests us because it provides a flexible and extensible interoperability format for transferring data between applications. Its success has led to wide cross-platform support, and you can now find Atom libraries in all popular languages, including Java and C#.
Atom represents data as lists, called feeds. Feeds are made up of one or more timestamped entries, which associate document metadata with web content.
The structure of an Atom document is defined in the Atom specification (RFC 4287), but the content of a feed will vary depending on our domain’s requirements. On the human Web, it might be blog posts or news items, whereas for computer-to-computer interactions, it might be stock trades, system health notifications, payroll instructions, or representations of coffee orders.
To illustrate the Atom format, let’s share a list of coffee orders between a cashier, ...