goals: uniform processing

void apply(Context*); 
void save (  State*); 
void load (  State*); 
void sync (     UI*); 
void validate();
When classes have similar inheritance and update signatures, they can be handled generically by managing code decoupled from their specifics.

Reader approves, as the strategy becomes one of the system conventions-- even unfamiliar code looks familiar.

This is a meta-pattern, whose power flows from the use of common sub-patterns like context, declare sync apply, and group plugin. 2017 [171108]