> ISO 639, the International Standard for language codes, badly needs > revision. So what is a language?
For XML and RDF, the authoritative list is the IANA Language Subtag Registry (7.7k languages, scripts, etc). See here for links http://vocab.getty.edu/doc/#IANA_Language_Tags and some software to parse it to a table. It also allows you to define your own extensions, which we had to use in some cases, e.g. http://vocab.getty.edu/doc/#GVP_Language_Tags http://www.lexvo.org/ provides detailed info about 7k languages, scripts, regions of use, etc.
