ModelMapper is basically a Java Function with the signature Function<T, Optional<R>>. Keeping this in mind, a ModelMapper simply returns one object for another. Headless Server features two ModelMapper functions, the richTextModelMapper and the dateModelMapper. Both are invoked by the CompositeModelMapper class, which in turn is delegated by the FilteringModelMapper. The FilteringModelMapper invokes a list of Predicates, if applicable, to filter the resolved content. The FilteringModelMapper is also the topmost ModelMapper and is also called the rootModelMapper.