Was King Arthur a King by Definition?

Current research in knowledge representation distinguishes between descriptional and assertional interpretations of semantic nets. This paper explores theoretical and applicative problems, which arise from that distinction in a historic domain. A prolog implementation of KL-ONE is used as a vehicle to compare the various alternatives available to represent knowledge related to single elements of the domain insertion or not of this knowledge in semantic nets in their descriptional sense. The final section of the paper discusses the problem in relation to the theories concerning the functioning of proper names from a logical and philosophical point of view.