SYLLABUS FOR 1997 WINTER

John McCarthy
Computer Science Department
Stanford University
Stanford, CA 94305
jmc@cs.stanford.edu
http://www-formal.stanford.edu/jmc/

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Abstract:

CS323 covers primarily logical AI with emphasis on the epistemology (often called ontology these days) and nonmonotonic reasoning.

I'm not sure how rigorously I will follow this syllabus. There will definitely be some additional readings, and some topics may take longer to cover than planned.

The 19 lectures will cover topics approximately as follows:

1. Approaches to AI. Biological approach that imitates the human, computer science that looks at the problems the world presents. The logic approach that emphasizes facts more than programs. Epistemology and heuristics. Some history. Nonmonotonic reasoning, context and other extensions to mathematical logic. Importance of the common sense informatic situation. How far to human-level AI? Reading: [McC58], Optional: [McC96a].
2. Logic for AI (Lifschitz's simple blocks world example). Logical languages, interpretations, models. Intended and unintended models. Preread: [Lif87],[Lif96a],[Lif96b].
3. Situation Calculus: [MH69] is the original reference. Preread: (1) The section Formalism (on situation calculus (that name came later)) from [MH69] (2) [McC58]
4. Frame problem and monotonic frame axioms. We will emphasize the blocks world. Relevant formulas are in [] . Preread: the sections Introduction and The frame problem(s) [SS94]
5. Continuation of blocks world formalization. Frames as objects. Exercises on situation calculus.
6. Philosophical issues. Semantics of ``can''. The practice of AI requires taking sides in certain longstanding philsophical controversies. For example, a person designing a computer program to learn about the world has to regard the world as more than a construct in the ``mind'' of the computer program. Otherwise, how could he compare the beliefs the program will come to have with facts about the world. Lots more philosophy is involved, but maybe AI people will do all right without thinking much about the conundrums philosophers have created for themselves. Preread: (1) section on ``can'' from [MH69], (2) [McC79a]
7. Contexts as formal objects. It is a truism that the meanings of sentences and terms depend on context. The meaning of a context is itself contextual, and you can carry this as far as seems useful. The innovation here is a formal theory of the relations of different contexts and how meanings depend on context. Preread: [McC93]
8. Elaboration tolerance. Preread: McCarthy-Amir drafts : [McC96c], [MA96], [Ami97] This is a new topic, but it relates to the continual computer science desire for modularity. We are studying how to make logical formalisms that allow changes in axiomatizations of phenomena without having to start all over. Our Drosophila is the missionary and cannibals problem. The point is to see what variants can be made purely by adding to the original statement.
9. Approximate concepts and approximate theories. Many important concepts, perhaps most, are intrinsically approximate in that they cannot be given if-and-only-if definitions. We study how statements involving approximate concepts can have definite truth values. The semantics of approximate concepts may be different from what is standard in mathematical logic. Reading to come.(***)
10. First order theories of individual concepts and propositions. We treat individual concepts and propositions as first class objects. This lets us say more about them than can be said using them just as terms and formulas of first order logic. Preread: [McC79b]
11. Heuristics: We would like to have a declarative theory of heuristics so programs can reason about them. Most likely we won't have more than illustrative examples of heuristics and hits at making them into objects. Reading to come, maybe.
12. Formalization of knowledge Preread: [Hal95]
13. Circumscription (1). Circumscription is a form of non-monotonic reasoning based on minimizing predicates and formulas. Preread: [McC80],[McC86]
14. Circumscription (2) Preread: [Lif93]
15. Default Logic is the second major surviving form of non-monotonic reasoning. Preread: [Rei80]
16. Nonmonotonic theories of action Preread: sections 3,4,6 in [SS94]
17. Introspection for Robots. Like people, robots will need to think about their own mental states, e.g. about their own intentions. Preread: [McC96b]

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