In computing, the feed: URI scheme (sometimes referred to, imprecisely, as the feed protocol; see Protocol (computing)) is a non-standard URI scheme designed to facilitate subscription to web feeds; specifically, it is intended that a news aggregator be launched whenever a hyperlink to a feed: URI is clicked in a web browser.

The scheme is used to flag a document in a syndication format such as Atom or RSS. The document is served over HTTP.

Critics hold that the purpose of the feed: URI scheme is better served by MIME types,^[1] or that it is not a user-friendly solution for the problem of feed subscription, since a user who has not installed the appropriate software will receive an unhelpful browser error message on clicking a link to a feed: URI.

The feed: URI scheme is currently supported by several popular desktop aggregators, including NetNewsWire, FeedDemon, Safari, and Flock, although as of 2006^[update] no effort seems to be underway to officially register the scheme with a standards body.

[edit] Syntax

The syntax for a feed: URI may be expressed in Backus–Naur form as follows:

 <feed_uri> ::= "feed:" <absolute_uri> | "feed://" <hier_part> 

Specifically, a feed: URI may be formed from any absolute URI (such as an absolute URL) by prepending feed:, and as a special case, may be formed from any absolute http: URI by replacing the initial http:// with feed://. Therefore, the following are two examples of valid feed: URIs:

 feed://example.com/entries.atom feed:https://example.com/entries.atom 

There is also a proposed extension of the syntax that supports metadata and embedded instructions to the aggregator.^[2]

[edit] References

1. ^ Nemerson, Evan (September 10. 2004). "On the feed:// URI scheme". Archived from the original on Jun 14, 2006. http://web.archive.org/web/20060614182102/http://www.coeus-group.com/en/archives/187-On-the-feed-URI-scheme.html. Retrieved 2009-06-04. 
2. ^ "FEED PROTOCOL - What are rss: and feed: links ?". brindys. http://www.brindys.com/winrss/feedformat.html. Retrieved 2009-06-04. 

[edit] External links

• The feed URI scheme — pre-draft version of a specification from 2004
• The feed protocol format — including proposal for extensions