Guid / rdf:about

Definition:

• RSS 2.0: "guid stands for globally unique identifier. It's a string that uniquely identifies the item. When present, an aggregator may choose to use this string to determine if an item is new."
  
  
• RSS 1.0: " {item_uri} must be unique with respect to any other rdf:about attributes in the RSS document and is a URI which identifies the item."
  
  

Example:

• <guid>http://intertwingly.net/slides/2003/seybold/</guid>
  
  
• <item rdf:about="http://intertwingly.net/slides/2003/seybold/">