From Steeple

The <s:id> element allows the specification of additional identifiers for this media item on a variety of services: Typically a media item would be posted to different 'media channels' and <s:id> allows you to specify and refer to those channels.

The element also allows content providers to specify alternative id for use by a remote aggregator.

[edit] 1 Examples

  <s:id domain="http://sms.cam.ac.uk" name="University of Cambride Streaming Media Service" href="http://drax.csi.cam.ac.uk/collection/535809">535809</s:id>  
  <s:id domain="http://www.youtube.com" name="YouTube" href="...">...</s:id>
  <s:id domain="http://www.itunes.com/itunesu" name="iTunesU" href="...">...</s:id>

The aggregator flags that the item is available on that service, allowing users to view the item on various other services.

[edit] 2 Specification

<s:id domain="http://sms.cam.ac.uk" name="University of Cambride Streaming Media Service" href="http://drax.csi.cam.ac.uk/collection/535809">535809</s:id>

where

• 'domain' specifies the url at which the service itself can be found (e.g. the front page of a portal)
• 'name' is the name of that service
• 'href' provides a link to the item on that service, ideally to a viewable web page ("text/html")
• the element data provides the id for the item on that service

[edit] 3 Further examples

[edit] 3.1 Use with a remote aggregator

Also, this element can be used to specify an id for the aggregator service, e.g. a feed coming from Cambridge may have this element

  <s:id domain="http://podcast.steeple.org.uk" name="Steeple aggregator">sms.cam.ac.uk-535809</s:id>

for use by the http://podcast.steeple.org.uk aggregator. The aggregator requires that the id conforms to its requirements, but if it does, the id is used, and the item can be found under that id.

[edit] 3.2 Use by an Opencast Matterhorn-like application

An application like Matterhorn might automatically post items to various services (like iTunesU and YouTube). The s:id element can be used by Matterhorn to provide links and ids for the media item on those services, allowing an aggregator of Matterhorn feeds to refer to the items on iTunesU / YouTube.