icbm namespace got created in a blog post for RSS 2.0, the Semantic Web Interest Group of the W3C devised a Basic Geo Vocabulary that allows for something very similar to ICBM addresses, but that does not require missiles and is integrated into RDF. It also adds the ability to specify an optional altitude, in meters.
+ This is meant to be used in RDF, so you would probably normally use this in a RSS 1.0 feed, but as with many other RDF namespaces, nothing really stops you from integrating that into RSS 2.0 or Atom, and many people have done so already.
++<rss version="2.0" xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#"> + <channel> + <!-- ... --> + <geo:lat>30.0301</geo:latitude> + <geo:long>32.5776</geo:longitude> + + <item> + <!-- ... --> + <geo:lat>31.5077090</geo:latitude> + <geo:long>-82.3115156</geo:longitude> + <!-- It's Moon time. --> + <geo:alt>384400000</geo:alt> + </item> + </channel> +</rss> ++
Two years later, in April 2005, GeoURL.org, a service that used to allow finding websites by their associated geographical location, introduced the geourl namespace, adding another duplicate namespace on top of icbm and geo. I mention it here too because the W3C validator supports all three namespaces!
You can use it with xmlns:geourl="http://geourl.org/rss/module/" and the <geourl:latitude> and <geourl:longitude> elements. I would however advise against using it as it increases the complexity for feed parser and feed reader developers; prefer the RDF geo namespace instead, which is more widely known.
And as a last piece of advice, do not mix the icbm, geo and geourl namespaces within the same channel or item, even if you intend to represent multiple coordinates at the same time! There are more complex but more flexible alternatives, which we will see in later posts, that allow to go beyond a single point.