Creating relations btw subcategories across category schemas

We have a need to map the sub-categories in a category schema to sub-categories in another category schema using the RAM Java API. For example, TMForum defines a mappings document between the categories of the telecom SID and eTOM models. If the SID and eTOM models are defined as 2 category schemas in RAM, how do you map the sub-categories in SID to the sub-catgories in eTOM schema? Other IBM products like InfoShpere Business Glossary allow you to map between hierarchies using custom attributes but we couldn't find any methods on the RAM Java API that help you map between sub-categories across category schemas.