It is possible you may want to be able to “Track” many websites whose contents change on a very unpredictable schedule. You can use RSS or ATOM.
RSS or Really Simple Syndication is a “Format” for delivering regularly changing web content. The feeds can be automated and can be channeled into a filtered display and the privacy is ensured as the tracking party need not subscribe to any email based newsletters.
Atom Syndication format is an xml based format used for feeds and AtomPub or APP or Atom Publishing Protocol is used for updating the resources.
Read the Details and differences at:
http://www.intertwingly.net/wiki/pie/Rss20AndAtom10Compared
http://www.intertwingly.net/wiki/pie/Rss20AndAtom10Compared
