# What are machine tags?
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, well, 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=straup
* flora:tree=coniferous
* medium:paint=oil
* geo:quartier="plateau mont royal"
* geo:neighbourhood=geo:quartier
