Generalize fraction quantities

[GordianDziwis]

I think the current approach to fractions does not scale well. A quality fraction can be a part of anything. For example, I would like to add qualities for fractions of elements in an alloy, this would add many classes to the ontology: copper mass fraction, iron mass fraction etc.

This concept of fractions of something could also be modeled with a relation like: <MassFraction> <fractionOf> <copper>

Did you already try this approach?