> I am not sure I see how you want to achieve that beyond Wikidata at
> this moment?
My comment referred only to Wikidata.
Then I think that we were not talking about the same things... what I meant is, restricting myself to chemical databases, ChEBI and ChemSpider have old fashion identifiers and IRIs (based on those identifiers), but HMDB, for example, does not. That's outside Wikidata's control, so Wikidata has to accept both types of identifiers. Right?