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AIC Seminar Series

Semantics for Autonomy and Interdependence in Agents

Carl Hewitt

Notice:  Hosted bt Richard Waldinger

Date:  Thursday, November 3rd 2005 at 2:30pm

Location:  EJ228  (Directions)


In this talk I use Participatory Semantics for autonomy and interdependence in agents. It is based on Actor semantics (which in turn is based on physics) where Actors are the universal primitives of concurrent digital computation. In response to a message that it receives, an Actor can make local decisions, create more Actors, send more messages, and determine how to respond to the next message received. A serializer is an Actor that is continually open to the arrival of messages. A distinguishing characteristic of the Actor model is that every message sent to a serializer must arrive although this can take an unbounded amount of time. The Actor model has a theory that can be used to express and sometimes verify properties of Actor systems as well as a semantics which assigns a denotation to each Actor system which is an infinite mathematical object that defines all the possible behaviors of the system. By these means commitments (defined to be information about Actor systems) can be expressed, conversed, negotiated and sometimes verified. For example systems that behave as scientific communities can have properties of monotonicity, concurrency, commutativity, and pluralism. Actors rise to the level of “agenthood” when they competently use expressions of commitments [which are increasingly standardized in the syntax of (binary) XML] expressing intention, dedication, judgment, decision, proposal, plan, contract, purpose, belief, policy, method, procedure, practice, backing, questioning, etc. Speech Act Theory has attempted to formalize the semantics of some kinds of expressions for commitments. Participatory Semantics can overcome some of the lack of expressiveness and generality in Speech Act Theory. Traditionally mathematical logic has been used for the semantics of expressions. However, the semantics of mathematical logic suffers from difficulties including the following: · Unruly combinatorics (General mathematical theorem proving has been intractable in practice although verification has been more successful.) · Semantic failure of proof theory and model theory in the face of inconsistency (I claim that all very large knowledge bases about human information system commitments are inconsistent.) · Inability to implement concurrent computation. (Mathematical logic can implement sequential and some kinds of parallel computation, e.g., the lambda calculus, but not concurrent computation as in the Actor model. The reason is that because of the quantum indeterminacy principle, it is not possible to deduce which message will arrive next when an Actor is concurrently sent multiple messages.) These failures do not mean that we should not use mathematical logic. We just have to be more clever in the way in which we use mathematical logic with regard to commitments. Participatory Semantics of commitments provides means for studying issues of autonomy and interdependence in agents. Interdependence can be manifested in conversation and negotiation with others; autonomy in reasoning.

   Bio for Carl Hewitt

Carl is known for his design of Planner that was the first Artificial Intelligence programming language based on procedural plans that were invoked using pattern-directed invocation from assertions and goals. Using program schemas in collaboration with Mike Paterson, Carl proved that recursion is more powerful than iteration and that parallelism is more powerful than recursion. In collaboration with Henry Baker, he published physical laws for computation which they then used to derive the continuity criterion for computable functions of Dana Scott. Using Participatory Semantics, he recently proved that coroutines are more powerful than recursion and that concurrency is more powerful than parallel coroutines. More recently Carl has worked to integrate sociology, anthropology, organization science, the philosophy of science, and services science into information science. He is also working on the Ultraconcurrency(TM) brand of massive concurrency, the subject of a May 2005 seminar at Stanford and an October 2005 seminar at Berkeley.

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