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Agent Communication Michael Floyd SYSC 5103 – Software Agents November 13, 2008

Agent Communication Michael Floyd SYSC 5103 – Software Agents November 13, 2008. Outline. Speech Acts Shared Ontology Agent Communication Language. Speech Acts. Speech act theory: communication is an action Action attempts to influence environment (other agents) ‏

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Agent Communication Michael Floyd SYSC 5103 – Software Agents November 13, 2008

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  1. Agent CommunicationMichael FloydSYSC 5103 – Software AgentsNovember 13, 2008

  2. mfloyd@sce.carleton.ca Outline • Speech Acts • Shared Ontology • Agent Communication Language

  3. mfloyd@sce.carleton.ca Speech Acts • Speech act theory: communication is an action • Action attempts to influence environment (other agents)‏ • No guarantee of success, just like any other action • Not the same master-slave relation as in programming -> a.method(message)‏

  4. mfloyd@sce.carleton.ca Theory of Speech Acts • Speech changes the state of the world • “I now pronounce you man and wife” • “The meeting is at noon”

  5. mfloyd@sce.carleton.ca Aspects of Speech Acts • Locutionary act – the act of uttering the words • “Please make me some tea.” • Illocutionary act – what is done in saying the words • A request for tea to be made • Perlocution act – what is done by saying the words • Someone made you tea

  6. mfloyd@sce.carleton.ca Aspects of Speech Acts (2)‏ • The hearer must: • Parse the message • Infer the same meaning as the sender • “Could you pass me the salt?” • Willfully want to perform the action • Is doing this in line with my goals or even possible?

  7. mfloyd@sce.carleton.ca Classes of Speech Acts (Searle)‏ • Representatives • try and get the hearer to believe something (claim, insist, etc.)‏ • Directives • a command to attempt to get the hearer to do something (request, forbid, etc.)‏ • Commissives • commit the speaker to a course of action (promise, vow, etc.)‏ • Expressives • express a psychological state (thank, congratulate, etc.)‏ • Declaratives • Declare a change in the world (wed, baptize, define, etc.)‏

  8. mfloyd@sce.carleton.ca Speech Acts in a Plan Request(Speaker, Hearer, act)‏ Preconditions: • Speaker believes Hearer can perform act or Speaker believes Hearer believes it can perform act • Speaker believes it wants act to be performed • Speaker believes Hearer wants act to be performed Effect: • Speaker believes Hearer wants to perform act

  9. mfloyd@sce.carleton.ca Shared Ontology • The communicating agent should agree to a terminology • Allows the agents to communicate in a consistent manner • For example, is a bat a baseball bat or an animal bat?

  10. mfloyd@sce.carleton.ca Agent Communication Languages • Standardized and structured languages for agents to communicate with each other • Examples: • KQML • FIPA • COOL • Boissier/Demazeau's Interaction Language • CMIP

  11. mfloyd@sce.carleton.ca Knowledge Sharing Effort (KSE)‏ • Two main deliverables from this project • Knowledge Interchange Format (KIF) • content of the message • Knowledge Query and Manipulation Language (KQML) • the illocutionary act of the message • with the content in KIF

  12. mfloyd@sce.carleton.ca KIF • Uses logic to define: • Properties of things • Tom is a vegetarian • Relationships between things • Tom and Janine are married • Properties of the domains • Everyone has a mother

  13. mfloyd@sce.carleton.ca KIF Examples (= (temperature m1) (scalar 83 Celsius))‏ The temperature, m1, is a scalar equal to 83 Celsius.

  14. mfloyd@sce.carleton.ca KIF Examples (2)‏ (defrelation bachelor (?x) := (and (man ?x) (not (married ?x))))‏ ?x is a variable and if ?x is a man and not married, then ?x is a bachelor

  15. mfloyd@sce.carleton.ca KIF Example (3)‏ (defrelation person (?x) :=> (mammal ?x))‏ If ?x is a person it is also a mammal.

  16. mfloyd@sce.carleton.ca KQML • A message between agents • Each message has a performative and a number of parameters • Used as an “envelop” around content (like KIF)‏

  17. From: A Proposal for a new KQML Specification By: Yannis Labrou and Tim Finin.

  18. mfloyd@sce.carleton.ca KQML Parameters :sender sender of the message :receiver intended recipient :content content of the message :language the language of the content :ontology the terminology of the message :reply-with identifier for the reply (if one is needed)‏ :in-reply-to reference to the reply-with

  19. mfloyd@sce.carleton.ca Example #1 – Initial Message (ask-one :sender trader-agent :receiver stock-server :language LPROLOG :ontology NYSE-TICKS :reply-with q1 :content (PRICE IBM ?price)‏ )‏

  20. mfloyd@sce.carleton.ca Example #1 - Response (tell :sender stock-server :receiver trader-agent :language LPROLOG :ontology NYSE-TICKS :in-reply-to q1 :content (PRICE IBM 14)‏ )‏

  21. mfloyd@sce.carleton.ca Example #2 – Initial Message (stream-about :sender A :receiver B :language KIF :ontology motors :reply-with q2 :content m1 )‏

  22. mfloyd@sce.carleton.ca Example #2 – Responses (1)‏ (tell :sender B :receiver A :language KIF :ontology motors :in-reply-to q2 :content (= (torque m1) (scalar 12 kgf))‏ )‏

  23. mfloyd@sce.carleton.ca Example #2 – Responses (2)‏ (tell :sender B :receiver A :language KIF :ontology motors :in-reply-to q2 :content (= (status m1) normal)‏ )‏

  24. mfloyd@sce.carleton.ca Example #2 – Responses (3)‏ (eos :sender B :receiver A :in-reply-to q2 )‏ Tells agent A that the stream of responses is done.

  25. mfloyd@sce.carleton.ca Criticism of KQML • No guarantee different implementations would interoperate • Performatives had meanings defined using english, so open to interpretation • No commissive performatives • The performatives set was overly large

  26. mfloyd@sce.carleton.ca Foundation for Intelligent Physical Agents • FIPA ACL was a an attempt to address shortcomings of KQML • FIPA ACL messages are very similar to KQML messages (inform :sender agen1 :receiver agent2 :content (price good2 150)‏ :language s1 :ontology hpl-auction )‏

  27. mfloyd@sce.carleton.ca FIPA • Aims for more formal message semantics • Semantics provided in a formal language : SL • SL allows the representation of beliefs, desires and uncertain beliefs

  28. mfloyd@sce.carleton.ca FIPA (2)‏ <i, inform(j, φ)> feasibility precondition: Biφ ۸ ¬Bi(Bifjφ ٧ Uifjφ )‏ rational effect: Bjφ Pre: Agent i believe φ and does not believe that j has a firm belief about φ or is uncertain about φ Post: Agent j should believe φ (hopefully)‏

  29. mfloyd@sce.carleton.ca References • Chapter 8 of “An Introduction to Multiagent Systems”, Michael Wooldridge

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