RSS Question

I'm confused as to whether an RSS aggregator on a client checks for updated content using the client's time presets (e.g. check every 10 minutes), or the web server with the RSS feed "pushes" out notifications of updated content as the updates are made? I get the feeling from this definition that RSS updates are handled by the client, but from Andy's comments to a previous post I gather that RSS updates are pushed by the RSS server to the client independent of the client's settings. The article Andy referenced makes me think either of the two is possible. Can RSS feeds be pushed and pulled from the servers where they are stored, or is it one way and not the other? I hope I don't sound too confusing.

Comments

[F. Andy Seidl]

Using the terms "RSS" and "notification" in the same sentence can be a little confusing. You are correct that a typical RSS client (i.e., aggregator or newsreader) periodically polls an RSS server for the latest RSS feed. The client then determines which items are new (to you) and synthesizes a "notification", which may be a blinking tray icon, a pop-up "toaster", a bolded item in a news window, etc.

Strictly speaking, RSS is simply an XML dialect--a way to serialize metadata about information resources. Thus, RSS specifies an information interchange format. It does not specify a "transport" mechanism. Most often, the RSS is transported over HTTP using GET operations; that is, a client performs a GET operation to poll for the latest RSS content (giving rise to a pun--RSS: I Get It, see http://www.cafepress.com/rsstore ). But, RSS can be transported using different mechanisms. For example, an RSS document could be "pushed" over HTTP using an HTTP POST operation. It could also be sent to a web service using a SOAP interface.

So, when I speak of using as a notification mechanism, I'm thinking more of RSS as a standardized interchange format with the understanding that RSS is most often (today) transported via HTTP GET but that other transport mechanisms are possible (and likely to emerge).