Till now I was using following method to determine subject specific RDF Type.
getBeanSession().getBeanMappingCache().getRdfTypeFromClass(bean.getClass()).toString());

This would work only if there is one specific active Rdf Type per subject. Moreover, providing capability to add multiple rdf types would help to achieve simple inferencing capability. e.g. all the sub types can marked as common rdf type, search on common rdf type would give all the sub types.

Jeff suggests API like following would be useful to manage multiple rdf types per subject.
Collection<Resource> getTypes(Resource subject); // All the types for the subject
void addType(Resource subject, Resource type); // adding a type
void removeType(Resource subject, Resource type); // removing a type
boolean hasType(Resource subject, Resource type); // existence of a type
Resource getActiveType(Resource subject); //<-- the call you asked about.