  This paper discusses the use of `ontologies' in Natural Language Processing.
It classifies various kinds of ontologies that have been employed in NLP and
discusses various benefits and problems with those designs. Particular focus is
then placed on experiences gained in the use of the Upper Model, a
linguistically-motivated `ontology' originally designed for use with the Penman
text generation system. Some proposals for further NLP ontology design criteria
are then made.
