Flattened tree hierarchy for learning content schema

learning-content-schema-improved.js

{
  byId: {
    'entity-id': {
      //Any of Class, Subject, Module or any other entity  
    }
  },
  subjects: {
    byClass:  {
      'class-id-1': ['class-id-1-subject-id-1', 'class-id-1-subject-id-2',...],
      'class-id-2': ['class-id-2-subject-id-1', 'class-id-2-subject-id-2',...],
    }
  },
  modules: {
    byClass:  {
      'class-id-1': ['class-id-1-module-id-1', 'class-id-1-module-id-2',...],
      'class-id-2': ['class-id-2-module-id-1', 'class-id-2-module-id-2',...],
    }
    bySubject:  {
      'subject-id-1': ['subject-id-1-module-id-1', 'subject-id-1-module-id-2',...],
      'subject-id-2': ['subject-id-2-module-id-1', 'subject-id-2-module-id-2',...],
    }
  }
}