Intelligent Agents: Technology and Applications

Agent Communications

IST 597BSpring 2003John Yen

Learning Objective Given a multi-agent application, be able to

design agent communication schemes.

Given an agent communication action, be able to describe its underlying semantics.

Problem (5%) Intel, AMD, and several other PC chip makers

have established a consortium to establish a virtual market place (VMP). The vision is that each company can create agents to go into this VMP to interact with other up-stream agents (representing the suppliers) for quotes and with down-stream agents (representing the PC makers) for sales forecast.

Your team is asked to identify key technical issues involved in establishing such a VMP.

Agent Communication

KIF: A language for the “content” of general agent communication

KQML: A language for the “message structure” of agent communication

Standards for agent communication protocols (e.g., DAML/S).

KIF

Knowledge Interchange Format A standard logic-based language for

describing an agent’s questions and answers Produced by a Knowledge Sharing Effort

funded by Defense Advanced Project Agency

Initially designed for agents to share what they know

KQML Knowledge Query and Manipulation

Language It describes the “speech act” of the message

using a set of performatives. Each performantive has required and

optional arguments. The content language of the message is not

part of KQML, but can be specified by KQML performatives.

An Example

(stream-all:content “(PRICE ?my-profolio ?price)”:receiver stock-server:language LPROLOG:ontology NYSE)

The stream-all performative asks a set of answers to be turned into a stream of replies.

KQML Performatives It describes the speech acts of the message. It specifies the communication protocol to

be used. Classified into seven categories.

An Example of Protocol A ---- monitor -----> B A <---- ready --------- B A ------ next ---------> B A <----- reply --------- B …. A ----- discard -------> B

Categories of Performatives Basic Query: Evaluate, ask-if, ask-about,

ask-one, ask-all Multi-response Query: stream-about,

stream-all, eos Response: reply, sorry Generic information: tell, achieve, cancel,

untell, unachieve

Categories of Performatives Generator: standby, ready, next, rest,

discard, generator Capability-definition: advertise,

recommend, subscribe, monitor, import, export

Networking: register, unregister, forward, broadcast, route

Capability-definition Performatives Advertise: Announce what kinds of

information requests the agent can handle(advertise

:ontology NYSE:language LOOM:content (monitor :content (PRICE ?x ?y)))

Recommend: Ask for recommendations of agents that can handle a particular kinds of information requests.

Protocols with Facilitator Agents

F: facilitator F <--- advertise(x) ---- BA --- recommend(x) --> F A <--- reply(B) ----- F A ------------------- monitor ----------------> B….

Semantics of Communication Actions Enable us to compose more complicated

communicative actions from primitive ones. Enable an agent to reason about the mental

states of the other agents involved in the communications.

Facilitates a more principled approach to establish communication protocol.

Semantics of Communication Actions

Attempt for the speaker to establish a mutual belief with the addressee

Semantics of Assert Performative (Cohen & Levesque) The speaker attempts to establish a joint

belief with the receiver that– The speaker believes the information

Whether the receives accept the belief depends on the reply (accept or reject)

Semantics of ProAssert The speaker attempts to establish a joint

belief with the receiver that– The speaker believes the information– The speaker believes that the receiver needs the

information

Semantics of ProAssert An attempt for the speaker (s) to establish a joint

belief that 1. S believes in the information (p)2. S believes that the receiver (a) needs the information.

0 0 0Pr ( , , , , ') ( , , ) ( , ( , , '), )

( , (Pr ), ( ') ( , , ),'' ( '' ') ({ , }, , ''), , , '),

( '' ') . ( , ( , ( , ( , ,b b

oAssert s a p t t Bel s p t Bel s Need a p t tAttempt s e oAssert t t t t Bel a p tt t t t MB s a P t t t whereP t t t t IntTh s Bel a Bel s p Need a p t

1 1 1

'), ), ), , , ( , ( , , ), )),

( ') ( , ( , , ), )

bb a a

t tt t Bel s t Bel a p t tt t t t Bel s Need a p t t

Responses to ProAssert

Three possible responses to ProAssert: Accept: The receiver believes the information Reject1: The receiver refuses the information

because the information is contradictory to its beliefs.

Reject2: The receiver refuses the information because it believes it does not need the information