FIPA Communicative Acts (CA)

1. FIPA Communicative Acts (CA)

2. Introduction to FIPA • FIPA is an IEEE Computer Society standards organization that promotes agent-based technology and the interoperability of its standards with other technologies. • FIPA, the standards organization for agents and multi-agent systems was officially accepted by the IEEE as its eleventh standards committee on 8 June 2005.

3. FIPA was originally formed as a Swiss based organization in 1996 to produce software standards specifications for heterogeneous and interacting agents and agent based systems. 

4. Since its foundations, FIPA has played a crucial role in the development of agents standards and has promoted a number of initiatives and events that contributed to the development and uptake of agent technology.

5. Furthermore, many of the ideas originated and developed in FIPA are now coming into sharp focus in new generations of Web/Internet technology and related specifications.

6. In March 2005, the FIPA Board of Directors presented this opportunity to the entire FIPA membership, who unanimously voted to join the IEEE computer Society. Now, it is time to move standards for agents and agent-based systems into the wider context of software development.

7. In short, agent technology needs to work and integrate with non-agent technologies. To this end, the IEEE Computer Society has formally accepted FIPA to become part of its family of standards committees.

8. Speech act (communicative act) Speech act theory has been influential in computer science since the early 1980s, particularly in the design of artificial languages for communication between software entities ("agents"). [wikipedia]

9. The theory was used, for example, to give a semantics to Agent Communication Language (ACL), an agent language developed by FIPA. The FIPA ACL speech act semantics, expressed semi-formally using epistemic modal logic, defines utterances in ACL in terms of the: certain beliefs, uncertain beliefs, desires and intentions of the speaker.

10. In principle, therefore, it enables agents using FIPA ACL to be sure that other agents will understand the meaning of utterances in the same way as the speaker. However, the FIPA ACL language syntax and semantics, although now widely used in agent systems, have been heavily criticized on theoretical and practical grounds.

11. Semantic Language (SL) Formalism • Components of the formalism: p, p1, ... are taken to be closed formulas denoting propositions, φ and ψ are formula schemas, which stand for any closed proposition, i and j are schematic variables which denote agents | = φ means that φ is valid.

12. Modal operators: • Belief (B) • Bip: i believes (that) p (for a proposition) holds • Uncertainty (U) • Uip: i is uncertain about p, but thinks that p is more likely than ￢p • Choice (C) • Cip: i desires that p currently holds

13. Action expressions: • a1 ; a2 • sequence in which a2 follows a1 • a1 | a2 • nondeterministic choice, in which either a1 happens or a2, but not both.

14. Notation • A CA model will be presented as follows: <i, act (j, C)> FP (Feasibility Precondition): φ1 RE (Rational Effect): φ2 • Translation of the above example: (act :sender i :receiver j :content C )

15. Underlying Semantic Model • Rational Effect (RE) • reasons for which the act is selected • Feasibility Preconditions (FPs) • conditions that have to be satisfied for the act to be planned (qualifications of the act).

16. Accept Proposal • Summary • The action of accepting a previously submitted proposal to perform an action. • Content • A tuple consisting of an action expression denoting the action to be done, and a proposition giving the conditions of the agreement.

17. Formal Model • <i, accept-proposal (j, <j, act>, φ))> • Example • Agent i informs j that it accepts an offer from j to stream a given multimedia title to channel 19 when the customer is ready. • (accept-proposal :sender (agent-identifier :name i) :receiver (set (agent-identifier :name j)) :in-reply-to bid089 :content "((action (agent-identifier :name j) (stream-content movie1234 19)) (B (agent-identifier :name j) (ready customer78)))" :language fipa-sl ) act φ

18. Agree • Summary • The action of agreeing to perform some action, possibly in the future. • Content • A tuple, consisting of an action expression denoting the action to be done, and a proposition giving the conditions of the agreement.

19. Formal Model • <j, agree (i, <j, act>, φ))> • Example • Agent i requests j to deliver a box to a certain location; j answers that it agrees to the request but it has low priority. • (agree :sender (agent-identifier :name j) :receiver (set (agent-identifier :name i)) :content "((action (agent-identifier :name j) (deliver box017 (loc 12 19))) (priority order567 low))" :in-reply-to order567 :protocol fipa-request :language fipa-sl ) act φ

20. Cancel • Summary • The action of one agent informing another agent that the first agent no longer has the intention that the second agent perform some action. • Content • An action expression denoting the action that is no longer intended.

21. Formal Model • <i, cancel (j, act)> • Example • Agent i asks j to cancel a previous request-whenever act by quoting the action. • (cancel :sender (agent-identifier :name i) :receiver (set (agent-identifier :name j)) :content "((action (agent-identifier :name i) (request-whenever :sender (agent-identifier :name i) :receiver (set(agent-identifier :name j)) :content2 \"((action (agent-identifier :name j) (inform-ref … :langage fipa-sl …) act

22. Call for Proposal • Summary • The action of calling for proposals to perform a given action. • Content • A tuple containing an action expression denoting the action to be done, and a referential expression defining a single-parameter proposition which gives the preconditions on the action.

23. Formal Model • <i, cfp (j, <j, act>, Ref x φ(x))> • Example • Agent i asks j to submit its proposal to sell 50 boxes of plums to i. • (cfp :sender (agent-identifier :name i) :receiver (set (agent-identifier :name j)) :content "((action (agent-identifier :name j) (sell plum 50)) (any ?x (and (= (price plum) ?x) (< ?x 10))))" :ontology fruit-market :language fipa-sl ) act Ref x φ(x)

24. ?x ?x denotes the value referred to by the reference X

25. Confirm • Summary • The sender informs the receiver that a given proposition is true, where the receiver is known to be uncertain about the proposition. • Content • A proposition.

26. Formal Model • <i, confirm (j, φ)> • Examples • Agent i confirms to agent j that it is, in fact, true that it is shining today. • (confirm :sender (agent-identifier :name i) :receiver (set (agent-identifier :name j)) :content "weather (today, shining)" :language Prolog ) φ

27. Disconfirm • Summary • The sender informs the receiver that a given proposition is false, where the receiver is known to believe, or believe it likely that, the proposition is true. • Content • A proposition.

28. Formal Model • <i, disconfirm (j, φ)> • Example • Agent i, believing that agent j thinks that a shark is a mammal and attempts to change j’s belief. • (disconfirm :sender (agent-identifier :name i) :receiver (set (agent-identifier :name j)) :content "((mammal shark))" :language fipa-sl ) φ

29. Failure • Summary • The action of telling another agent that an action was attempted but the attempt failed. • Content • A tuple, consisting of an action expression and a proposition giving the reason for the failure.

30. Formal Model • <i, failure (j, a, φ)> • Example • Agent i informs j that it has failed to open a file. • (failure :sender (agent-identifier :name i) :receiver (set (agent-identifier :name j)) :content "((action (agent-identifier :name i) (open \"foo.txt\")) (error-message \"No such file: foo.txt\"))" :language fipa-sl ) a φ

31. Inform • Summary • The sender informs the receiver that a given proposition is true. • Content • A proposition.

32. Formal Model • <i, inform (j, φ )> • Examples • Agent i informs agent j that (it is true that) it is raining today. • (inform :sender (agent-identifier :name i) :receiver (set (agent-identifier :name j)) :content "weather (today, raining)" :language Prolog ) φ

33. Inform If • Summary • A macro action for the agent of the action to inform the recipient whether or not a proposition is true. • Content • A proposition.

34. Formal Model • <j, inform-if (i, φ)> • Examples • Agent i requests j to inform it whether Lannion is in Normandy. • (request :sender (agent-identifier :name i) :receiver (set (agent-identifier :name j)) :content "((action (agent-identifier :name j) (inform-if :sender (agent-identifier :name j) :receiver (set (agent-identifier :name i)) :content \"in( lannion, normandy)\" :language Prolog)) )" :language fipa-sl ) φ

35. Inform Ref • Summary • A macro action for sender to inform the receiver the object which corresponds to a reference, for example, a name. • Content • An object description (a referential expression).

36. Formal Model • <j, inform-ref (i, Ref x δ(x))> • Example • Agent i requests j to tell it the current Prime Minister of the United Kingdom. • (request :sender (agent-identifier :name i) :receiver (set (agent-identifier :name j)) :content "((action (agent-identifier :name j) (inform-ref :sender (agent-identifier :name j) :receiver (set (agent-identifier :name i)) :content \"((iota ?x (UKPrimeMinister ?x)))\" :ontology world-politics :language fipa-sl)))" :reply-with query0 :language fipa-sl ) Ref x δ(x)

37. iota (ιninth Greek character) • When using the definite descriptor in a formal logical context, it is common to denote it by the symbol iota: ψ(ιx(φx)) ≔ ∃x(∀y(φy ↔ y = x) ∧ ψx) Ref: Wikipedia

38. Not Understood • Summary • The sender of the act (for example, i) informs the receiver (for example, j) that it perceived that j performed some action, but that i did not understand what j just did. A particular common case is that i tells j that i did not understand the message that j has just sent to i. • Content • A tuple consisting of an action or event, for example, a communicative act, and an explanatory reason.

39. Formal Model • <i, not-understood(j, a, φ)> • Examples • Agent i did not understand a query-if message because it did not recognize the ontology. • (not-understood :sender (agent-identifier :name i) :receiver (set (agent-identifier :name j)) :content "((action (agent-identifier :name j) (query-if :sender (agent-identifier :name j) :receiver (set (agent-identifier :name i)) :content \"<fipa-ccl content expression>\" :ontology www :language fipa-ccl)) (unknown (ontology \"www\")))" :language fipa-sl) a φ

40. Propagate • Summary • The sender intends that the receiver treat the embedded message as sent directly to the receiver, and wants the receiver to identify the agents denoted by the given descriptor and send the received propagate message to them. • Content • A tuple of a descriptor, that is, a referential expression, denoting 1) an agent or agents to be forwarded the propagate message, 2) an embedded ACL communicative act, that is, an ACL message, performed by the sender to the receiver of the propagate message and 3) a constraint condition for propagation, for example, a timeout.

41. Formal Model • <i, propagate (j, Ref x δ(x), <i, cact>, φ)> • Example • Agent i requests agent j and its federating other brokerage agents to do brokering server. • (propagate :sender (agent-identifier :name i) :receiver (set (agent-identifier :name j)) :content "((any ?x (registered (agent-description :name ?x :services (set (service-description :name agent-brokerage)))) (action (agent-identifier :name i) (proxy :sender (agent-identifier :name i) :receiver (set (agent-identifier :name j)) :content … )) (< (hop-count) 5))“ :ontology brokerage-agent-ontology …) Ref x δ(x) cact φ

42. Propose • Summary • The action of submitting a proposal to perform a certain action, given certain preconditions. • Content • A tuple containing an action description, representing the action that the sender is proposing to perform, and a proposition representing the preconditions on the performance of the action.

43. Formal Model • <i, propose (j, <i, act>, φ)> • Example • Agent i proposes to j to sell 50 boxes of plums for $5 • (propose :sender (agent-identifier :name i) :receiver (set (agent-identifier :name j)) :content "((action i (sell plum 50)) (= (any ?x (and (= (price plum) ?x) (< ?x 10))) 5)" :ontology fruit-market :in-reply-to proposal2 :language fipa-sl ) act φ

44. Proxy • Summary • The sender wants the receiver to select target agents denoted by a given description and to send an embedded message to them. • Content • A tuple of a descriptor, that is, a referential expression, that denotes 1) the target agents, 2) an ACL communicative act, that is, an ACL message, to be performed to the agents, and 3) a constraint condition for performing the embedded communicative act, for example, the maximum number of agents to be forwarded, etc.

45. Formal Model • <i, proxy (j, Ref x δ(x), <j, cact>, φ)> • Example • Agent i requests agent j to do recruiting and request a server. • (proxy :sender (agent-identifier :name i) :receiver (set (agent-identifier :name j)) :content "((all ?x (registered(agent-description :name ?x :services (set (service-description :name video-on-demand))))) (action (agent-identifier :name j) (request … :ontology vod-server-ontology :language FIPA-SL true)“ :ontology brokerage-agent :protocol fipa-recruiting …) Ref x δ(x) cact φ

46. Query If • Summary • The action of asking another agent whether or not a given proposition is true. • Content • A proposition.

47. Formal Model • <i, query-if (j, φ)> • Example • Agent i asks agent j if j is registered with domain server d1. • (query-if :sender (agent-identifier :name i) :receiver (set (agent-identitfier :name j)) :content "((registered (server d1) (agent j)))" :reply-with r09 … ) φ

48. Query Ref • Summary • The action of asking another agent for the object referred to by a referential expression. • Content • A descriptor (a referential expression).

49. Formal Model • <i, query-ref (j, Ref x δ(x))> • Example • Agent i asks agent j for its available services. • (query-ref :sender (agent-identinfier :name i) :receiver (set (agent-identifier :name j)) :content "((all ?x (available-service j ?x)))" … ) Ref x δ(x)

50. Refuse • Summary • The action of refusing to perform a given action, and explaining the reason for the refusal. • Content • A tuple, consisting of an action expression and a proposition giving the reason for the refusal.