I contacted the ILO about using this classification structure on Wikipedia I thought it could be useful as a recognized category structure They were very helpful and granted me hereinafter called the Licensee a nonexclusive nontransferable worldwide licence to reproduce the structure and framework of the ILO International Standard Classification of Occupations ISCO for use in the online free encyclopaedia Wikipedia wwwwikipediacom accessible by the general public hereinafter called the endusers   However one of the conditions of the licence was that The rights are granted on the understanding that any republication by the endusers in whatever form without the written consent by the ILO is prohibited the Licensee undertakes to so inform its endusers   Although there were other restrictions I think this one may preclude using the structure at all I will follow this up over at the copyright issue pages