[Zope] Interface for Topic Index

Hi, I would like to let a user create a Topic List (in Tree form) and later choose out of it to assign topics to a stx document product I made. These topics will allow to search a ZCatalog later on. Is there already someone who made such an interface, which I can easely import and use? Anybody ideas what the easiest way is for such a thing? Thanks in advance, Tom.