Non-monotonic Reasoning

Reasoning in which adding premises may invalidate previously derivable conclusions. Required for default reasoning, exception handling, and business rules where new information retracts tentative conclusions.

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Summary

McCarthy’s 1975 memo (revived in 1998 with footnotes anticipating XML and electronic commerce) sketches a Common Business Communication Language (CBCL) allowing computers from different organizations to exchange business messages - requests for quotations, offers, order status, delivery queries - without pre-arranged bilateral formats. The paper enumerates requirements: open-endedness, pre-existing compatibility, independence of internal data formats, and ability to fall back to human-readable form when a receiver does not understand a new message.

He proposes messages as nested parenthesized lists (a Lisp-like syntax McCarthy argues is isomorphic to but simpler than XML), adjectival modifiers (ADJECTIVE FOO YELLOW), and Russell description operators for referring expressions. The essay prefigures KQML-style performatives and electronic data interchange, and closes with 1998 advice to XML, W3C, and ICE on extensibility, Lisp-style syntax, and standard time formats.

Key Ideas

Inter-organizational computer communication without pre-arranged formats.

Lisp-style S-expression syntax isomorphic to but simpler than XML.

Adjectival modifiers (ADJECTIVE x y as a kind of y) for partial understanding.

Non-monotonic reasoning required for natural-language-like expressivity.

Proto-KQML vision of semantic business messaging.

Conceptual Contribution

Claim: Organisations should exchange business messages in a common, open-ended language without pre-arranged bilateral formats; partial understanding must degrade gracefully to human-readable fallback.

Mechanism: Lisp-style S-expression messages (isomorphic to but simpler than XML), adjectival modifiers (ADJECTIVE x y) for partial-match semantics, Russell description operators for referring expressions, non-monotonic reasoning for NL-like expressivity; 1998 footnotes advise XML/W3C/ICE communities.

Concepts introduced/used: Common Business Communication Language, S-expressions, EDI, Non-monotonic Reasoning, Adjectival Modifiers, Agent Communication Languages, Ontologies, Performatives, Speech Act Theory, KQML

Stance: foundational

Relates to: Anticipates the performative-based vision of KQML Language And Protocol and the open discovery ambitions of Agent Network Protocol / Survey Of Agent Interoperability Protocols; its syntactic minimalism resonates with REST’s uniform interface in Principled Design Of The Modern Web Architecture.