Common knowledge: Now you have it, now you don`t?
- IBM Almaden Research Center, San Jose, CA (United States)
- Weizmann Institute of Science, Rehovot (Israel)
- Rice Univ., Houston, TX (United States)
The notion of common knowledge, where everyone knows, everyone knows that everyone knows, etc., has proven to be fundamental in various disciplines, including Philosophy, Artificial Intelligence, Economics, and Psychology. This key notion was first studied by the philosopher David Lewis in the context of conventions. Lewis pointed out that in order for something to be a convention, it must in fact be common knowledge among the members of a group. (For example, the convention that green means {open_quotes}go{close_quotes} and red means {open_quotes}stop{close_quotes} is presumably common knowledge among the drivers in our society.) Common knowledge also arises in discourse understanding. Suppose Ann asks Bob {open_quotes}What did you think of the movie?{close_quotes} referring to a showing of Monkey Business they have just seen. Not only must Ann and Bob both know that {open_quotes}the movie{close_quotes} refers to Monkey Business, but Ann must know that Bob knows, Bob must know that Ann knows that Bob knows, and so on. In fact, by a closer analysis of this situation, it can be shown that there must be common knowledge of what movie is meant in order for Bob to answer the question appropriately. Finally, common knowledge also turns out to be a prerequisite for agreement and coordinated action in distributed systems. This is precisely what makes it such a crucial notion in the analysis of interacting groups of agents. On the other hand, in practical settings common knowledge is impossible to achieve. This puts us in a somewhat paradoxical situation, in that we claim both that common knowledge is a prerequisite for agreement and coordinated action and that it cannot be attained. We discuss two answers to this paradox: Modeling the world with a coarser granularity, and relaxing the requirements for coordination.
- OSTI ID:
- 466449
- Report Number(s):
- CONF-9610138-; CNN: Contract F49620-91-C-0080; TRN: 97:001309-0029
- Resource Relation:
- Conference: International multi-disciplinary conference on intelligent systems: a semiotic perspective, Gaithersburg, MD (United States), 21-23 Oct 1996; Other Information: PBD: 1996; Related Information: Is Part Of Intelligent systems: A semiotic perspective. Volume I: Theoretical semiotics; Albus, J.; Meystel, A.; Quintero, R.; PB: 303 p.
- Country of Publication:
- United States
- Language:
- English
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