Syndication
License statements may be included in various synication formats, generally at the feed and item level, where the latter overrides the former.
RSS 1.0
http://web.resource.org/rss/1.0/modules/cc/
RSS 2.0
http://backend.userland.com/creativeCommonsRssModule
Atom 1.0
http://ietfreport.isoc.org/idref/draft-snell-atompub-feed-license/
Human-visible notice
Some podcast players display the contents of a copyright
element found in a feed. Example usage, not really intended to be machine-parsable, customize for communication with human readers, but do include URL of the relevant CC license and most importantly URL where users can get back to your site:
- <copyright>All the songs in this podcast, and the podcast itself, are licensed to the public under http://creativecommons.org/licenses/by-nc-sa/1.0/ verify at http://magnatune.com/info/openmusic</copyright>
Licensed Content Discovery
Not all feeds include license metadata. In psuedocode, here are heuristics for discovering licensed content via feeds, perhaps useful in particular for aggregators.
function feedItemLicense(feedItem) { # license found for feed item URL (e.g., rel="license")? if (feedItem.license() != null) { return feedItem.license(); } # license found at feed top level? if (feedItem.feed().license() != null) { return feedItem.feed().license(); } # no explicit license in feed, fetch feed item URL feedItemContent = httpGet(feedItem.itemURL()); if (parseLicenseFromHTML(feedItemContent) != null) { return parseLicenseFromHTML(feedItemContent); } # no license found in content at feed item URL, fetch # item referred to in enclosure if there is one, # look for embedded metadata if (feedItem.enclosure() != null) { enclosureContent = httpGet(feedItem.enclosure()); return parseLicenseFromMedia(enclosureContent); }
This is obviously just a sketch. Aggregators may wish to use different heuristics for different feeds. Different aggregators will want to be more or less aggressive -- e.g., many will not want to go through the step of downloading and attempting to parse enclosure content. See Content Curators for some sites with feeds of CC licensed content.