Thad Guidry, 13/09/2016 19:38:
There is no need, therefore, to replicate those same definitions in Wikidata by creating a new Wikidata item (topic / entity) for each external vocabulary class or subclass or property.
Instead, the best practice is to simply POINT to those external definitions, such as those in Schema.org, DBPedia.org, MusicBrainz, etc., etc.
Agreed. If the external definition is compatible, just link it. A specific item needs to be created only where the two definitions are incompatible. I would define two items to be equivalent iff swapping them doesn't change the truthness of any statement or inference on Wikidata (https://en.wikipedia.org/wiki/Equivalence_relation#Well-definedness_under_an... ). Makes sense?
I don't know if Q474191 and Q26869695 are incompatible definitions; I understood you claimed they were. If the two definitions are compatible, we can merge the two items and just consider Q474191 equivalent to SchemaOrg's definition of "Diet".
Nemo