CASE-ROLEs are EVENT-STATE-RELATIONs and are not special in any sense. From the point of view of the ontology, there is no distinction at all between CASE-ROLEs and the so called domain-relations. We have eleven CASE-ROLEs and corresponding CASE-ROLE-INVERSEs defined in the ontology. They are: AGENT, THEME, INSTRUMENT, EXPERIENCER, BENEFICIARY, ACCOMPANIER, PURPOSE, LOCATION, SOURCE, DESTINATION, and PATH. CASE-ROLE-INVERSEs have corresponding names obtained by appending -OF to names of CASE-ROLEs. The domains of CASE-ROLEs are all EVENTs except in the case of LOCATION whose domain also includes OBJECT. The range of most CASE-ROLEs is in some subclass of OBJECTs except in the case of PURPOSE whose range is in EVENTs also. The domain of EXPERIENCER has been specifically restricted to PASSIVE-COGNITIVE-EVENTs and INVOLUNTARY-PERCEPTUAL-EVENTs. Since we do not have a separate means CASE-ROLE, the range of INSTRUMENT can be both EVENT or OBJECT.
It may be noted that there are no co-roles. It is assumed that they can all be handled using appropriate set notations.
Kavi Mahesh