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Tags add metadata to web pages and multimedia, allowing for sorting and location. Triple tags have a defined syntax with three elements: namespace, predicate, and value. They are useful for geotagging and evolving as a folksonomy. Consistent character definitions apply.
One use of tags is as a tool for adding metadata to something, such as a web page or instance of multimedia, such as an image. Metadata, defined as data about data, adds a description to an item that is managed separately from, but linked to, the item. With a photograph, for example, metadata tags can identify where the photograph was taken, photographer, camera and lens used, time of day, identity of people and/or buildings in photography, etc. Metadata is also useful for locating and sorting items. A triple tag, also known as a machine tag, is a specialized type of tag that was first created in 2004 for Geolicious, later adopted by Mappr and GeoBloggers, and dubbed the machine tag in January of 2007 when it was officially adopted by Flickr®.
A triple tag has a defined syntax and three elements, hence the name triple tag. The generic form looks like this:
Namespace: predicate=value
The namespace defines the realm of the tag. The predicate is a property of the namespace. And the value is a particular instance of that property in that namespace.
One common use is identifying your location, sometimes called geotagging. Geotagging looks like this, with the appropriate number replaced by the parenthesis:
geo:lat=(number)
geo:long=(number)
The number can be positive or negative, in which case a hyphen/minus precedes it.
As the triple tag system is evolving as a folksonomy – where individuals evolve tags as needed, instead of being established as a hierarchy, where a standardized set of tags are set and shared for consistency – tags with the same meaning may use synonyms, rather than the same terms, while different taggers might also use the same term but with different meanings. The character definitions appear to be consistent, however. The namespace and predicate, which are case-insensitive, must each start with a letter a–z. The following characters can be a–z, 0–9, and underscores. Values can contain any value used by a plain vanilla tag, but if spaces are included, the value must be enclosed in quotes.
