Hi Erik,
did you have a look at the ABAP Doc for the method registry->register_discoverable_resource()?
category_scheme => Schema, can be seen as a name space for term
category_term => Term which allows clients to identify the collection. The combination of category + term has to result in a unique key which allows the client to retrieve the collection URL.
Here an example from the discovery entry for ABAP Classes:
category_scheme = http://www.sap.com/adt/categories/oo
category_term = classes
Have a look at the discovery document via the communication log. It should give you some ideas on how to pick your scheme/term.
cheers
Thomas