This is an experiment - for now.
NSManagedObjectModel *model = buildCoreDataModel(
withEntities(
Entity(@"Book").withAttributes(
Attribute(@"title").withType(NSStringAttributeType), nil
),
Entity(@"Page"),
nil
),
withRelationShips(
RelationShip(@"pages").from(@"Book").to(@"Pages"), nil
),
nil
);