Machine tags are tags that use a special syntax to define extra information about a tag. Machine tags have a namespace, a predicate and a value. The namespace defines a class or a facet that a tag belongs to ('geo', 'flickr', etc.) The predicate is name of the property for a namespace ('latitude', 'user', etc.) The value is, the value. Like tags, there are no rules for machine tags beyond the syntax to specify the parts of a machine tag. For example, you could tag a photo with flickr:user=otis

Graphing tags for a link over time

Lets people map real-life objects in the city and view them on an online map