Content is often syndicated from many blogs, social websites and news services in computer-readable feeds that can be used by other people and systems. For example, content from newspapers is often syndicated so that news headlines can be read by people in their own feed reader programs or integrated into their own websites.
Previous to syndication, semi-regular visits to bookmarked sites resulted in a lack of accuracy in monitoring information. Now, feed aggregators or readers allow you to check multiple blog or news feeds on a regular basis, and you can choose to view only new or updated posts since your last access. You can pull information from sites and put it directly into your desktop (Thunderbird) or browser application (Google Reader, Bloglines), allowing you to quickly scan for relevant content. Intelligent pushing of feeds (e.g. with “pingback”) can also be facilitated to update content immediately on aggregator sites (e.g. PlanetPlanet) or other applications.
The most common syndication format used is “RSS”, which has various meanings (Really Simple Syndication, Rich Site Summary and RDF Site Summary) and comes in different flavours (currently there are eight variations). They all share the same basic principles: the latest articles, with hyperlinks, titles and summaries, are syndicated using a computer-readable format (XML or RDF). In general, one does not have to worry about which feed format a blog or website provides, because practically any aggregator or news reader will be able to read it anyway. However, the RSS 1.0 variant (in RDF) allows us to combine syndicated articles with metadata from other vocabularies such as FOAF or Dublin Core.
The RSS feed structure is as follows:
- Class “channel”:
- Properties “title”, “link”, “description”
- Contains “items”
- Class “item”:
- Properties “title”, “link”, “description”, “date”, “creator”, etc.
The strength of RSS is in its generality, but therein lies its weakness: when one is subscribed to multiple channels or items, there is no way to easily group by different types of content based on the available metadata. RSS is used for more than just blog headlines and news syndication, having applications in libraries (e.g. to announce new book acquisitions), shared calendars (RSSCalendar.com), recipe clubs, etc. Executives in many corporations are also starting to mandate what RSS feeds they wants their companies to provide.
Similar to RSS is the Atom Syndication Format, an XML format that is also commonly used for syndicating web feeds (e.g. from Blogger.com). The Atom Publishing Protocol (APP or AtomPub for short) is related to this, being a simple HTTP-based protocol for creating and modifying web resources, and the specification was edited by Joe Gregorio and Bill de hÓra.