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October, 2009 School of Computing andInformatics, University of Nairobi

MSC COMPUTER SCIENCE

INTER-AGENT COMMUNICATION (Wooldridge)

Session Topics

1.Role of communication

2.Speech acts

3.Plan based semantics

4.Knowledge query and manipulation language (KQML)

5.Knowledge Interchange Format (KIF)6.Foundation for Intelligent Physical Agents (FIPA)

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October, 2009 School of Computing andInformatics, University of Nairobi

MSC COMPUTER SCIENCE

INTER-AGENT COMMUNICATION (Wooldridge)

Communication is a macro-aspectof intelligent

agent technology. It involves relating the agentto the society, rather than the individual.

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October, 2009 School of Computing andInformatics, University of Nairobi

ICS 806 - MULTI-AGENT SYSTEMS

INTER-AGENT COMMUNICATION (Wooldridge)

Speech ActsSpeech act theory is a pragmatictheory of language. It is a theory of

language use. It attempts to give account of how language is used bypeople every day to achieve their goals and intentions.

Origin:- Austins 1962 book, How to Do Things with Words.

Austin noticed that some utterances are rather like physical actionsthat appear to change the state of the world.Paradigm examples would be:

declaring war; christening; I now pronounce you man and wife

Everythinguttered carry intentions of satisfying some goal or intention.

A theory of how utterances are used to achieve intentions is a speechact theory.

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October, 2009 School of Computing andInformatics, University of Nairobi

ICS 806 - MULTI-AGENT SYSTEMS

Types of speech actSearle (1969) identified various different types of speech act:

representatives: such as informing, e.g., It is raining

directives: attempts to get the hearer to do something e.g., pleasemake the tea

commisives: which commit the speaker to doing something, e.g.,I promise to. . .

expressives: whereby a speaker expresses a mental state, e.g.,

thank you!

declarations: match statements with environmental states such aswhen declaring war or christening.

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October, 2009 School of Computing andInformatics, University of Nairobi

ICS 806 - MULTI-AGENT SYSTEMS

Components of speech actIn general, a speech act can be seen to have two components:

1. performative verb: (e.g., request, inform, . . . )2. propositional content: (e.g., the door is closed)

Consider:speech act = please close the door

performative = request content = the door is closed

speech act = the door is closed! performative = inform content = the door is closed

speech act = is the door closed? performative = inquire content = the door is closed

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October, 2009 School of Computing andInformatics, University of Nairobi

Plan Based Semantics

Cohen & Perrault (1979) defined semantics of speech acts using theprecondition-delete-addlist formalism of planning research.

Note that a speaker cannot (generally) forcea hearer to accept

some desired mental state.Here is their semantics for request (s requests h to do):request(s, h, )pre:

sbelieves hcan do (you dont ask someone to do something unless you think they can do it) sbelieves hbelieves hcan do :(you dont ask someone unless theybelieve they can do it) sbelieves swants :(you dont ask someone unless you want it!)

post: hbelieves sbelieves swants : (the effect is to make them aware of your desire)

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KQML (knowledge query and manipulation language) and KIF(knowledge interchange format )These are agent communication languages (ACLs) which are

standard formats for the exchange of messages among agents.

The best known ACL is KQML, developed by thethe United StatesDefense Advanced Research Project Agency(DARPA) knowledge

sharing initiative.

KQML consists of two components:-1. the knowledge query and manipulation language (KQML);

2. the knowledge interchange format (KIF).

KQML is an outer language, that defines various acceptablecommunicative verbs, or performatives.

Example performatives: ask-if (is it true that. . . ) perform (please perform the following action. . . ) tell (it is true that. . . ) reply (the answer is . . . )

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October, 2009 School of Computing andInformatics, University of Nairobi

KIF(knowledge interchange format)

KIF is a language for expressing message content.

In order to be able to communicate, agents must haveagreed on a common set of terms. A formalspecification of a set of terms is known as a ontology.

Example KQML/KIF dialogue. . .A to B: (ask-if (> (size chip1) (size chip2)))B to A: (reply true)B to A: (inform (= (size chip1) 50))B to A: (inform (= (size chip2) 30))

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October, 2009 School of Computing andInformatics, University of Nairobi

FIPA(Foundation for Intelligent Physical Agents )

FIPA started work on a program of agent standardsIts basic structure is quite similar to KQML:

performative: 20 performative in FIPA.

housekeeping: e.g., sender etc.content:the actual content of the message.

Example

(inform:sender agent1:receiver agent5:content (price good200 150):language sl:ontology hpl-auction

)

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October, 2009 School of Computing andInformatics, University of Nairobi

Performatives in FIPA

Performative Passing inform.Requesting informationNegotiation Performing actions Error handling

Accept proposal x

Agree x

Cancel x x

Confirm proposal (Cfp) x

Confirm xDisconfirm x

Failure x

Inform x

Inform-if x

Inform-ref x

Not understood x

Propose x

Query-if x

Query-ref x

Refuse x

Reject-proposal x

Request x

Request-when x

Request-whenever x

subscribe x

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