P.S.
I think this has been suggested already but I am not sure - I think that one should eventually think of allowing parallel classifications schemes at wikidata. So one could have an ISO classification AND a user made classification like similar to the one at megajoule.org. Frankly speaking I fear that classifications like the one at megajoule.org (at least if I look at the 100 sofar inserted items, (see under technology)) may not be so overly appropriate for industrial applications. In particular their data model may be a problem.