RDF uses the RFC3066 standard for language tags for literals in natural languages. The revision RFC3066bis includes productive use of language, country and script codes. These form an implicit ontology of natural languages for marking-up texts. Relating each language tag with classes of appropriately tagged literals allows this implicit ontology to be made explicit as an ontology in OWL in which every class in the ontology is a datarange. The treatment extends to XML Literals, which may have multiple embedded language tags. Further features of RFC3066bis such as the relationship with deprecated codes, language ranges and language tag fallback can be expressed in OWL. A small change to the RDF model theory is suggested to permit access to the language tag in the formal semantics, giving this ontology a precise formal meaning. Illustrative use cases refer to use of English, Japanese, Chinese and Klingon texts.
Jeremy J. Carroll, Addison Phillips