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

2. November 13,2008mfloyd@sce.carleton.caSlide 2 Outline Speech Acts Shared Ontology Agent Communication Language

3. November 13,2008mfloyd@sce.carleton.caSlide 3 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. November 13,2008mfloyd@sce.carleton.caSlide 4 Theory of Speech Acts Speech changes the state of the world –“I now pronounce you man and wife” –“The meeting is at noon”

5. November 13,2008mfloyd@sce.carleton.caSlide 5 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. November 13,2008mfloyd@sce.carleton.caSlide 6 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. November 13,2008mfloyd@sce.carleton.caSlide 7 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. November 13,2008mfloyd@sce.carleton.caSlide 8 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. November 13,2008mfloyd@sce.carleton.caSlide 9 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. November 13,2008mfloyd@sce.carleton.caSlide 10 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. November 13,2008mfloyd@sce.carleton.caSlide 11 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. November 13,2008mfloyd@sce.carleton.caSlide 12 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. November 13,2008mfloyd@sce.carleton.caSlide 13 KIF Examples (= (temperature m1) (scalar 83 Celsius))‏ The temperature, m1, is a scalar equal to 83 Celsius.

14. November 13,2008mfloyd@sce.carleton.caSlide 14 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. November 13,2008mfloyd@sce.carleton.caSlide 15 KIF Example (3)‏ (defrelation person (?x) :=> (mammal ?x))‏ If ?x is a person it is also a mammal.

16. November 13,2008mfloyd@sce.carleton.caSlide 16 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. November 13,2008mfloyd@sce.carleton.caSlide 18 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. November 13,2008mfloyd@sce.carleton.caSlide 19 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. November 13,2008mfloyd@sce.carleton.caSlide 20 Example #1 - Response (tell :sender stock-server :receiver trader-agent :language LPROLOG :ontology NYSE-TICKS :in-reply-to q1 :content (PRICE IBM 14)‏ )‏

21. November 13,2008mfloyd@sce.carleton.caSlide 21 Example #2 – Initial Message (stream-about :sender A :receiver B :language KIF :ontology motors :reply-with q2 :content m1 )‏

22. November 13,2008mfloyd@sce.carleton.caSlide 22 Example #2 – Responses (1)‏ (tell :sender B :receiver A :language KIF :ontology motors :in-reply-to q2 :content (= (torque m1) (scalar 12 kgf))‏ )‏

23. November 13,2008mfloyd@sce.carleton.caSlide 23 Example #2 – Responses (2)‏ (tell :sender B :receiver A :language KIF :ontology motors :in-reply-to q2 :content (= (status m1) normal)‏ )‏

24. November 13,2008mfloyd@sce.carleton.caSlide 24 Example #2 – Responses (3)‏ (eos :sender B :receiver A :in-reply-to q2 )‏ Tells agent A that the stream of responses is done.

25. November 13,2008mfloyd@sce.carleton.caSlide 25 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. November 13,2008mfloyd@sce.carleton.caSlide 26 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. November 13,2008mfloyd@sce.carleton.caSlide 27 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. November 13,2008mfloyd@sce.carleton.caSlide 28 FIPA (2)‏ feasibility precondition: B i φ ۸ ¬B i (Bif j φ ٧ Uif j φ )‏ rational effect: B j φ 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. November 13,2008mfloyd@sce.carleton.caSlide 29 References Chapter 8 of “An Introduction to Multiagent Systems”, Michael Wooldridge