SNePS and Knowledge, Belief, & Intensionality

1. A sequence of 3 related papers on intensionality in SNePS:

   • Maida, Anthony S., & Shapiro, Stuart C. (1982), "Intensional Concepts in Propositional Semantic Networks", Cognitive Science 6: 291-330; reprinted in Ronald J. Brachman & Hector J. Levesque (eds.), Readings in Knowledge Representation (Los Altos, CA: Morgan Kaufmann, 1985): 169-189.

   • Rapaport, William J. (1986), "Logical Foundations for Belief Representation", Cognitive Science 10: 371-422.

     Abstract: This essay presents a philosophical and computational theory of the representation of de re, de dicto, 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. (A shorter version of this paper appeared as Rapaport & Shapiro 1984. Both are based on my SUNY Buffalo M.S. thesis.)

   • Rapaport, William J.; Shapiro, Stuart C.; & Wiebe, Janyce M. (1997), "Quasi-Indexicals and Knowledge Reports", Cognitive Science 21: 63-107.

     • Reprinted in Francesco Orilia & William J. Rapaport (eds.), Thought, Language, and On tology: Essays in Memory of Hector-Neri Castañeda (Dordrecht: Kluwer Academic Publishers, 1998): 235-294.

     • Abstract: We present a computational analysis of de re, de dicto, and de se belief and knowledge reports. Our analysis solves a problem first observed by Hector-Neri Castañeda, namely, that the simple rule

       `(A knows that P) implies P'

       apparently does not hold if P contains a quasi-indexical. We present a single rule, in the context of a knowledge-representation and reasoning system, that holds for all P, including those containing quasi-indexicals. In so doing, we explore the difference between reasoning in a public communication language and in a knowledge-representation language, we demonstrate the importance of representing proper names explicitly, and we provide support for the necessity of considering sentences in the context of extended discourse (for example, written narrative) in order to fully capture certain features of their semantics.

2. Three other papers that discuss the SNePS view of intensionality:
   Wiebe, Janyce M., & Rapaport, William J. (1986), "Representing De Re and De Dicto Belief Reports in Discourse and Narrative" [PDF], Special Issue on Knowledge Representation, Proceedings of the IEEE 74: 1405-1413.
   Abstract: Belief reports can be interpreted de re or de dicto; we investigate the disambiguation of belief reports as they appear in discourse and narrative. In earlier work, representations for de re and de dicto belief reports were presented, and the distinction between de re and de dicto belief reports was made solely on the basis of their representations. This analysis is sufficient only when belief reports are considered in isolation. We need to consider more complicated belief structures, in addition to those presented earlier, in order to sufficiently represent de re and de dicto belief reports as they appear in discourse and narrative. Further, we cannot meaningfully apply one, but not the other, of the concepts de re and de dicto to these more complicated belief structures. We argue that the concepts de re and de dicto do not apply to an agent's conceptual representation of her beliefs, but that they apply to the utterance of a belief report on a specific occasion. A cognitive agent interprets a belief report such as "S believes that N is F", or "S said, `N is F'" (where S and N are names or descriptions, and F is an adjective) de dicto if she interprets it from N's perspective, and she interprets it de re if she interprets it from her own perspective.
   • Shapiro, Stuart C., & Rapaport, William J. (1987), "SNePS Considered as a Fully Intensional Propositional Semantic Network", in Nick Cercone & Gordon McCalla (eds.), The Knowledge Frontier: Essays in the Representation of Knowledge (New York: Springer-Verlag): 262-315.

     Abstract: SNePS, the Semantic Network Processing System, is a semantic-network language with facilities for building semantic networks to represent virtually any kind of information, retrieving information from them, and performing inference with them. Users can interact with SNePS in a variety of interface languages, including a Lisp-like user language, a menu-based screen-oriented editor, a graphics-oriented editor, a higher-order-logic language, and an extendible fragment of English. This article discusses the syntax and semantics for SNePS considered as an intensional knowledge representation system, and provides examples of uses of SNePS for cognitive modeling, database management, pattern recognition, expert systems, belief revision, and computational linguistics.

   • Shapiro, Stuart C., & Rapaport, William J. (1991), "Models and Minds: Knowledge Representation for Natural-Language Competence", in Robert Cummins & John Pollock (eds.), Philosophy and AI: Essays at the Interface (Cambridge, MA: MIT Press): 215-259.

     Abstract: Cognitive agents, whether human or computer, that engage in natural-language discourse and that have beliefs about the beliefs of other cognitive agents must be able to represent objects the way they believe them to be and the way they believe others believe them to be. They must be able to represent other cognitive agents both as objects of beliefs and as agents of beliefs. They must be able to represent their own beliefs, and they must be able to represent beliefs as objects of beliefs. These requirements raise questions about the number of tokens of the belief representation language needed to represent believers and propositions in their normal roles and in their roles as objects of beliefs. In this paper, we explicate the relations among nodes, mental tokens, concepts, actual objects, concepts in the belief spaces of an agent and the agent's model of other agents, concepts of other cognitive agents, and propositions. We extend, deepen, and clarify our theory of intensional knowledge representation for natural-language processing, as presented in previous papers and in light of objections raised by others. The essential claim is that tokens in a knowledge-representation system represent only intensions and not extensions. We are pursuing this investigation by building CASSIE, a computer model of a cognitive agent and, to the extent she works, a cognitive agent herself. CASSIE's mind is implemented in the SNePS knowledge-representation and reasoning system.