User Application to build Material Hierarchy

Hi, I would like to help users to build a hierarchy without having to maintain the hierarchy externally on a spreadsheet and upload it. So I would like an application that would baskically present a list of materials and allow the user to drag the material to a hierarchy node.

1. Do most people just upload their hierarchies to create them?

2. Is there anything out there that would help the users build a hierarchy like I mentioned?

3. If I was to build this with Web Dynpro ABAP does anyone know any of the hierarchy tables I would need to populate or any of the standard classes I could use?

Thanks,