1. 1 Computer Science Department California Polytechnic State University San Luis Obispo, CA, U.S.A. Franz J. Kurfess CPE/CSC 580: Intelligent Agents 1

2. 2 © Franz J. Kurfess Usage of the Slides ◆ these slides are intended for the students of my CPE/CSC 580 “Intelligent Agents” class at Cal Poly SLO ◆ if you want to use them outside of my class, please let me know (fkurfess@calpoly.edu)fkurfess@calpoly.edu ◆ some of them are based on other sources, which are identified and cited ◆ I usually select a subset for each quarter, either by hiding some slides, or creating a “Custom Show” (in PowerPoint) ◆ to view these, go to “Slide Show => Custom Shows”, select the respective quarter, and click on “Show” ◆ To print them, I suggest to use the “Handout” option ◆ 4, 6, or 9 per page works fine ◆ Black & White should be fine; there are few diagrams where color is important

3. 3 © Franz J. Kurfess Course Overview ❖ Introduction  Intelligent Agent, Multi-Agent Systems  Agent Examples ❖ Agent Architectures  Agent Hierarchy, Agent Design Principles ❖ Reasoning Agents  Knowledge, Reasoning, Planning ❖ Learning Agents  Observation, Analysis, Performance Improvement ❖ Multi-Agent Interactions  Agent Encounters, Resource Sharing, Agreements ❖ Communication  Speech Acts, Agent Communication Languages ❖ Collaboration  Distributed Problem Solving, Task and Result Sharing ❖ Agent Applications  Information Gathering, Workflow, Human Interaction, E-Commerce, Embodied Agents, Virtual Environments ❖ Conclusions and Outlook

4. 4 © Franz J. Kurfess Overview Communication among Agents ❖ Motivation ❖ Objectives ❖ Communication  speech acts; agent communication languages ❖ Cooperation  self-interest, societal benefits ❖ Important Concepts and Terms ❖ Chapter Summary

5. 5 © Franz J. Kurfess Bridge-In

6. 6 © Franz J. Kurfess Pre-Test

7. 7 © Franz J. Kurfess Motivation

8. 8 © Franz J. Kurfess Objectives

9. 9 © Franz J. Kurfess Evaluation Criteria

10. 10 Communication Communication Basics Speech Acts Language: Syntax, Semantics, Pragmatics

11. 11 © Franz J. Kurfess Basic Concepts ❖ communication  exchange of information  requires a shared system of signs  greatly enhanced by language  speaker  produces signs as utterances  general: not only spoken language  listener (hearer)  perceives and interprets signs

12. 12 [Woolridge 2009] Communication among Agents

13. 13 © Franz J. Kurfess Purpose of Communication ❖ sharing of information among agents or systems  query other agents for information  responses to queries  requests or commands  actions to be performed for another agent  offer  proposition for collaboration  acknowledgement  confirmation of requests, offers  sharing  of experiences, feelings

14. 14 © Franz J. Kurfess Communication Problems ❖ intention  what is the expected outcome (speaker’s perspective) ❖ timing  when is a communication act appropriate ❖ selection  which act is the right one ❖ language  what sign system should be used ❖ interpretation  will the intended meaning be conveyed to the listener ❖ ambiguity  can the intention be expressed without the possibility of misunderstandings

15. 15 © Franz J. Kurfess Language and Communication ❖ Natural Language  used by humans  evolves over time  moderately to highly ambiguous ❖ Formal Languages  invented  rigidly defined  little ambiguity

16. 16 © Franz J. Kurfess Natural Language ❖ formal description is very difficult  sometimes non-systematic, inconsistent, ambiguous ❖ mostly used for human communication  easy on humans  tough on computers ❖ context is critical  situation, beliefs, goals

17. 17 © Franz J. Kurfess Formal Languages ❖ symbols  terminal symbols  finite set of basic words  not: alphabet, characters  non-terminal symbols  intermediate structures composed of terminal or non-terminal symbols ❖ strings  sequences of symbols ❖ phrases  sub-strings grouping important parts of a string

18. 18 © Franz J. Kurfess Formal Languages Cont. ❖ sentences  allowable strings in a language  composed from phrases ❖ grammar  rules describing correct sentences  often captured as rewrite rules in BNF notation ❖ lexicon  list of allowable vocabulary words

19. 19 © Franz J. Kurfess Communication Models ❖ encoded message model  a definite proposition of the speaker is encoded into signs which are transmitted to the listener  the listener tries to decode the signs to retrieve the original proposition  errors are consequences of transmission problems ❖ situated language model  the intended meaning of a message depends on the signals as well as the situation in which they are exchanged  mis-interpretation may lead to additional problems

20. 20 © Franz J. Kurfess Communication Types ❖ telepathic communication  speaker and listener have a shared internal representation  communication through Tell/Ask directives ❖ language-based communication  speaker performs actions that produce signs which other agents can perceive and interpret  communication language is different from the internal representation  more complex  involves several mappings  language needs to be generated, encoded, transmitted, decoded, and interpreted

21. 21 © Franz J. Kurfess Telepathic Communication [Russell & Norvig 1995]

22. 22 © Franz J. Kurfess Language-Based Communication [Russell & Norvig 1995]

23. 23 © Franz J. Kurfess Communication Steps: Speaker ❖ intention  decision about producing a speech act ❖ generation  conversion of the information to be transferred into the chosen language ❖ synthesis  actions that produce the generated signs

24. 24 © Franz J. Kurfess Communication Steps: Listener ❖ perception  reception of the signs produced by the speaker  speech recognition, lip reading, character recognition  analysis  syntactic interpretation (parsing)  semantic interpretation  disambiguation  selection of the most probable intended meaning  incorporation  the selected interpretation is added to the existing world model as additional piece of evidence

25. 25 © Franz J. Kurfess Communication Example [Russell & Norvig 1995] 25

26. 26 Speech Acts Basics Speech Act Theory Mappings Components Semantics

27. 27 © Franz J. Kurfess Speech Act ❖ used for the production of language ❖ independent of the communication mode  talking, sign language, typing, flags ❖ word  basic meaningful communicative sign  smaller entities may exist  e.g. syllable, phonem, letter  don’t carry meaning ❖ speaker (sender)  producer of an utterance ❖ hearer (listener, recipient)  consumer of an utterance

28. 28 © Franz J. Kurfess Speech Act Theory ❖ developed in linguistics, cognitive science, communication theory ❖ pragmatic theories of language  based on language use ❖ utterances  elementary speech actions  based on or related to intentions ❖ different typologies of speech acts

29. 29 [Woolridge 2009] 8-8 Speech Acts - Searle Searle (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., ‘please make the tea’  commissives: 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 war or christening

30. 30 [Woolridge 2009] 8-9 Speech Act Components a performative verb:  e.g., request, inform, promise, … propositional content:  e.g., “the door is closed”

31. 31 [Woolridge 2009] 8-10 Speech Act Mappings Speech act performatives & content:  performative = request content = “the door is closed” speech act = “please close the door”  performative = inform content = “the door is closed” speech act = “the door is closed!”  performative = inquire content = “the door is closed” speech act = “is the door closed?”

32. 32 [Woolridge 2009] Speech Act Semantics intention of the speaker  leads to a specific formulation of a statement interpretation by the listener  may be different from the intended meaning methods from other AI areas have been applied  e.g. planning

33. 33 Agent Communication Languages standard formats for the exchange of knowledge and information usually based on messages

34. 34 [Woolridge 2009] KQML KQML (Knowledge Query and Manipulation Language)  developed by the ARPA knowledge sharing initiative KIF (Knowledge Interchange Format)  designed to work in conjunction with KQML

35. 35 [Woolridge 2009] KQML and KIF KQML is an ‘outer’ language  defines various acceptable ‘communicative 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... ’) KIF is a language for expressing message content  related to knowledge representation languages

36. 36 [Woolridge 2009] KIF – Knowledge Interchange Format Used to state: Properties of things in a domain  e.g., “Orna is chairman” Relationships between things in a domain  e.g., “Michael is Yael’s boss” General properties of a domain  e.g., “All students are registered for at least one course”

37. 37 [Woolridge 2009] KIF Examples “The temperature of m1 is 83 Celsius”: (= (temperature m1) (scalar 83 Celsius)) “An object is a bachelor if the object is a man and is not married”: (defrelation bachelor (?x) := (and (man ?x) (not (married ?x)))) “Any individual with the property of being a person also has the property of being a mammal”: (defrelation person (?x) :=> (mammal ?x))

38. 38 [Woolridge 2009] KQML and KIF communication between agents requires a common set of terms  ontology formal specification of a set of terms knowledge sharing  requires defining common ontologies  OWL - Web Ontology Language  ontology editors Protégé

39. 39 [Woolridge 2009] KQML/KIF Dialogue Example A to B: (ask-if (> (size chip1) (size chip2))) B to A: (reply true) B to A: (inform (= (size chip1) 20)) B to A: (inform (= (size chip2) 18))

40. 40 [Woolridge 2009] Criticisms of KQML fluid performative set  leading to interoperability problems transport mechanisms not precisely defined semantics not rigorously defined missing commissives  performatives for making commitments performative set too large and ad hoc

41. 41 [Woolridge 2009] FIPA Agent Communication Language program of agent standards  initiated by the Foundation for Intelligent Physical Agents (FIPA)  the centerpiece is an ACL structure similar to KQML  performatives 20 performatives in FIPA  content the actual content of the message  housekeeping e.g., sender, receiver,...

42. 42 [Woolridge 2009] FIPA ACL Example Example: (inform :senderagent1 :receiveragent5 :content(price good200 150) :languagesl :ontologyhpl-auction )

43. 43 [Woolridge 2009] FIPA Performatives

44. 44 [Woolridge 2009] “Inform” and “Request” two basic performatives in FIPA  all others are macro definitions  defined in terms of “Inform” and “Request”. semantics of “Inform” and “Request”  pre-condition what must be true in order for the speech act to succeed  “rational effect” what the sender of the message hopes to bring about

45. 45 [Woolridge 2009] “Inform” pre-condition is that the sender  holds that the content is true  intends that the recipient believe the content  does not already believe that the recipient is aware of whether content is true or not content is a statement

46. 46 [Woolridge 2009] 8-24 “Request” pre-condition is that the sender:  intends action content to be performed  believes recipient is capable of performing this action  does not believe that receiver already intends to perform action content is an action

47. 47 © Franz J. Kurfess Post-Test

48. 48 © Franz J. Kurfess Evaluation ❖ Criteria

49. 49 © Franz J. Kurfess Summary Communication

50. 50 © Franz J. Kurfess Important Concepts and Terms ❖ agent ❖ Agent Communication Language ❖ alphabet ❖ ambiguity ❖ communication ❖ collaboration ❖ coordination ❖ formal language ❖ grammar ❖ hearer ❖ KIF ❖ KQML ❖ language ❖ lexicon ❖ listener ❖ multi-agent system ❖ natural language ❖ pragmatics ❖ recipient ❖ semantics ❖ sender ❖ sign ❖ speech act ❖ syntax ❖ utterance ❖ vocabulary

51. 51 © Franz J. Kurfess