Abstract
This essay presents a philosophical and computationol theory of the representation
of de re, de dlcto, nested, and quasi-indexical belief reports expressed in
natural language. The propositional Semantic Network Processing System
(SNePS) is used for representing and reasoning about these reports. In particular,
quasi-indicators (indexical expressions occurring in intentional contexts and
representing uses of indicators by another speaker) pose problems for natural language
representation and reasoning systems, because--unlike pure indicators
--they cannot be replaced by coreferential NPs without changing the meaning of
the embedding sentence. Therefore, the referent of the quasi-indicator must be
represented in such a way that no invalid coreferential claims are entailed. The
importance of quasi-indicators is discussed, and it is shown that all four of the
above categories of belief reports can be handled by a single representational
technique using belief spaces containing intensional entities. Inference rules and
belief-revision techniques for the system are also examined.