The type representing a generic ontology term. The type representing an IVOA UCD. TBD add reference The type representing a subject keyword from the "standard" list of keywords from ApJ/A&A/MNRAS/ ... The type representing an entry from the IVOA AstroObject ontology. TBD add reference The type representing an entry from the IVOA ontology of physical processes. TBD add reference and create that list ... The type representing an object that can be used in SNAP experiments to build a representation of the world. The type representing an entry from a list of names of identified objects. For example Simbad [TBD link] might provide this list. TBD do something about how to represent this further. String ? Restricts the OnbtologyObject in the sense of the usual inheritance, "is-a" relation.