Intelligent Agents: Technology and Applications Agent Communications IST 597B Spring 2003 John 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) ---- B A --- 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.

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