31// I added "Attributable". Does not feel like it keeps the interface minimal. However, the subpopulation attribute comes from it, which is used
32// rather centrally in the StrategyManager stuff, which is the place for which this interface exists. Also so far wasn't totally systematic there
33// since it was doing something for persons (subpopulation-based strategy) that it was not offering for others, forcing those who use StrategyManager
34// to implement Attributable seems like an acceptable burden. kai, may'19