Can ECS work with component hierarchies?

One of the good things with classical Unity is it's transforms and their ability to have a hierarchy of components and sub-components does Pure ECS have any kind of hierarchy features or is it better to use transforms?

 

You can setup hierarchy manually.

 

You can use IComponentData, ISharedComponentData, and FixedArray to store Entities, giving you the ability to create hierarchies in different ways depending on your needs. You can look at Unity.Transforms namespace as an example, as I believe they implemented hierarchies in there with the TransformParent component.