How To Discover RSS Feeds for a given URL
Found something that I wanted:
Google's AJAX Feed API has a load feed and lookup feed function (Docs here).
a) Load feed provides the feed (and feed status) in JSON
b) Lookup feed provides the RSS feed for a given URL
Theres also a find feed function that searches for RSS feeds based on a keyword.
Planning to use this with JQuery's $.getJSON
This link will allow you to validate the link against the RSS/Atom specifications using the W3C specs, but does require you to manually enter the url.
There are a number of ways to do this programmatically, depending on your choice of language - in PHP, parsing the file as valid XML is a good way to start, then compare it to the relevant DTD.
For b), if the link itself isn't a feed, you can parse it and look for a specified feed in the <head> section of the page, searching for a link whose type is "application/rss+xml", e.g:
<link rel="alternate" title="RSS Feed" href="http://www.example.com/rss-feed.xml" type="application/rss+xml" />This type of link is the one used by most browsers to "auto-discover" feeds (causing the RSS icon to appear in your address bar)