Agent Communication - Multi Agent Systems - Lecture Slides, Slides of Multiagent Systems

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Agent communication

Speech acts

• Most treatments of communication in multi-agent systems borrow their inspiration from speech act theory
• Speech act theories are pragmatic theories of language; they attempt to account for how language is used by people every day to achieve their goals and intentions.
• The origins of speech act theories are usually traced to J.L. Austin’s book “How to do things with words”.
• This is a philosophy book with a linguistic approach
• Not a computer science book!

Speech acts (cont’d)

• Searle (1969) identified various types of speech acts:
• Representatives
  • Such as informing: “It is raining”
• Directives
  • Attempts to get the hearer to do something, e.g. “please make 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:
  • Such as declaring a war

Speech acts (cont’d)

• There is some debate about whether this (or any!) typology of speech acts is appropriate
• In general, a speech act can be seen to have two components: - A performative verb (e.g. request, inform) - A propositional content (e.g. “the door is closed”)

Semantics of speech acts

• How can one define the semantics of a speech act?
• What is going to be the affect of the speech act to the world? - More exactly to the receiver?
• The sender agent can not (generally) force a receiver agent to accept some desired mental state.
• Different formalisms were proposed, depending on the representation of the world.

Plan based semantics

• Cohen & Perrault (1979) defined the semantics of speech acts using the precondition-delete-add list formalism of planning research.
• Semantics for a request: request(s, r, a)
• Preconditions:
  • S believes r can do h
    • You don’t ask someone to do something unless you think they cando it
  • S believes h believes h can do a
    • You don’t ask someone unless they believe they can do it
  • S believes S wants a
    • You don’t ask someone unless you want it
• Postconditions:
  • H believes s believes s wants a
    • The effect is to make them aware of your desire.

KQML

• Developed by the ARPA knowledge sharing initiative
• Composed of two parts:
• Knowledge Query and Manipulation Language (KQML) - KQML is an “outer language”, that defines various acceptable “communicative acts” or performatives - Many critics say there were too many performatives (>40)
• Knowledge Interchange Format (KIF) Docsity.com

FIPA ACL, introduction

• FIPA (Foundation for Intelligent Physical

Agents) non-profit organization

• Companies like IBM, Hitachi, HP, British Telecom, Siemens
• Universities and research institutes
• Started work on a program of agent standards,

the most important being the ACL (1997)

Example

(inform

:sender agent :receiver agent :content (price milk 100) :language sl :ontology hlp-auction

)

Performatives in FIPA

Inform

• The content is a statement
• Pre-conditions:
  • The sender holds that the content is true
  • Intends that the recipient believes the content
  • Does not already believe that the recipient is aware of whether the content is true or not.

Request

• The content is an action.
• Pre conditions:
  • The sender intends the action content to be performed
  • Believes the recipient is capable of performing the action
  • Does not believe that the sender already intends to perform the action.

Interaction protocols

• A standard set of messages needed to achieve a certain goal
• They are usually describing a time limited “conversation”

Protocols standardized by FIPA

• FIPA Request
• FIPA Query
• FIPA Request When
• FIPA Contract Net
• FIPA Iterated Contract Net
• FIPA English Auction
• FIPA Dutch Auction
• FIPA Brokering
• FIPA Recruiting
• FIPA Subscribe
• FIPA Propose Interaction Docsity.com