RDL as (better) OWL
The RDL is available as OWL already. You can download it from our version control system, or browse it at http://data.posccaesar.org/rdl/.
However, we are not very happy with the current data model: http://rds.posccaesar.org/2008/02/OWL/ISO-15926-2_2003
The data model was created in 2008 to reflect 15926 part 2 as an OWL ontology. A major concept in the model is reified relationships. This allowed the modellers to represent relationships that have relationships in a simple way.
Modelling the statement "all cars are vehicles" would use a specialisation relationship to make "car" a subclass of "vehicle".