Protocol Composition

1. Protocol Composition • Two main issues: • What are possible compositions • What are the correctness criterion • Representation of syntactic compositions • Π1;Π2 (sequence), • Π1|Π2 (non-deterministic OR), • Π1||Π2 (concurrent execution), • Π1* (repetition), • p?;Π2 (conditional execution) • Π[a/π] (embedding) • Any combination of the above • Question: Any other composition ?

2. Legality of Compositions • Completeness criterion • Complete: No un-discharged commitments • Incomplete: When goal is to create a commitment Enabling criterion • Question: When are these meaningful ? • Π1;Π2 • Π1|Π2 • Π1||Π2 • Possible to define several other criterions

3. Group Communication • Group communication is pervasive – We • Post messages to mailing lists, notice boards • Broadcast on radio and TV • Speak in meetings, classrooms • Publish textual material Key: We need not know whom we are talking to • Agents will need to communicate with groups • But, agent communication languages do not properly support group communication

4. The problem • Broadcasting is problematic for ACLs, and for speech act theory in general • E.g., FIPA ACL: • To inform/request a group of agents, communicate with them individually – problem with joint action. • Prereq. to an inform – speaker believes thehearer does not already believe the content • Prereq. to a request –speaker believes thehearer does not already intend to do Act But, in general, may not know who the hearer’s are For multicast – may not know who is in the group

5. Lessons from Natural Language • “Those of you who registered with the conference yesterday, please raise your hands” • Addressed to known group • Specific actors unknown • “Authorized personnel only” • Addressed to whoever reads the message • From whoever wrote the message (some authorized role) • Intended actors subset of intended addressees • “Becker, take attendance” sent to whole class • Request to Becker, but whole class knows it • “John and Betty Smith request the pleasure of your company at the wedding of their daughter…” • Request from a group

6. Constraints for ACLs • Addressee – communication to groups • Sender – communication by groups • Recipient – Overhearers, unintended recips. • Actor – actors =/= recipients • Actor Awareness – requester can be ignorant of identity of intended actors • Sender Awareness – sender can be ignorant of individual members of recipient group

7. Groups • Need to represent dynamic groups in the formal language • In most analyses of MK/MB, groups are not “part” of the logic E.g., when Ejis defined as the group G is not part of the language • Some logic that do include groups as part of the language, use it as a fixed set (Wooldridge, 2000). • Define the group by its characteristic function • Extend the formal language to use named groups (eg. Yankees)

8. Notation • τis a group having the characteristic predicate τ(z), where z is a free variable • ‘< …>’ indicates scope • Superscripts τz usedfor common variables • Let ‹› be a formula defined by the following rule: • If  is a formula without any term of the form τ, then ‹› =  • If  is a formula with term τ, and z does not appear in , and τ(z) is the property predicate that corresponds to τ, and (z) is a formula formed by replacing τ with z in , then ‹› = (z. τ(z) (z)) • ‘Underscore’ in τindicates a distributive reading

9. Notation (cont.) • For  containing a named group G, and when  contains no instance of z, replace G by z as follows: ‹› = $z. authorized-representative(z,G) Λ(z) where authorized-representative isa semantically primitive function Note: z could be a group as well ! Example: “AOL requests Time-Warner to merge the two companies” • Board of directors, sub-committee, etc.

10. Group Action • Distributive action -- everyone in the group does the action (we use τ) when we intend a group to be considered distributively (Done  a) ‹Done  a›= z (z)  (Done z a) • Collective action -- not clear who has to do something; depends on the type of action and circumstances. |= (Done  a) iff exists a element G of the power-set of agents y s.t. (y) and for all zG |= (Done z a) No underscore

11. Group Beliefs • Distributive belief -- group G believes p if everyone in G believes p. “The students of CSE 101 believe p” (BEL StudentsOfCSE101p) = z (student z CSE101)  (BEL z p) • Existential belief -- G believes p if one member of G believes p • Majority belief -- G believes p if most members of G believe p, etc. • Similarly for GOAL, Mutual Belief, etc.

12. Group mutual beliefs • Between an agent and a group (BMB x τp)  ‹BMB x τp› z τ(z)  (BMB x z p) • Between a group and an agent (BMBτ x p)  ‹BMBτ x p› z τ(z)  (BMB z x p) • Between two groups (BMBτ1τ2p)  ‹z‹wBMB1zτ2wp›› z τ1(z)  (BMB z τ2p) • Mutual belief (MB12p)  (BMB12p) Λ (BMB21p)

13. Approach to defining Speech Acts • We redefine the basic elements of C&L’90, Smith et al. 1996, to include: • PGOAL, Intend, PWAG, etc., replacing agents by possible groups • Particular instances supply specific groups τ, τ, etc. • Next, redefine the speech acts, showing that they do not require quantifications of group membership into agents’ beliefs • z τ(z)  (BEL x (Done z a)) • z quantifies into x’s belief • (BEL x (z τ(z)  (Done z a)) • z does not quantify into x’s belief • x believes whoever has property τ has done action a

14. Requesting (REQUEST α β γ e a q t)  (ATTEMPT α eφ ψ t) Where β = recipient(s) γ = actor(s) α = sender(s) φ = whoever are the γ’s do the action a, having formed the intention to do a because α has the goal that whoeverare the γ’s should do a. Ψ = mutual belief between whoever is/are the recipient(s) β and whoever is/are the sender(s) α that α will be committed to φ after e.

15. Requesting (simplified) (REQUEST α β γ e a q t)  (ATTEMPT α eφψ t) Where β = recipient(s) γ = actor(s) α = sender(s) φ = ‹z (Done γza) Λ [PWAG γz α (Done γza) q]› ψ = (BMB β α [PWAG α γ φq]) Example: Let recipients and actors be groups with characteristic predicates. Replace β and γ by βandγ respectively in the definition of request. (Goal α φ) = (Goal α z γ(z)  [(Done za) Λ [PWAG z α (Done za)]) (Intention α ψ) = (Intention α (BMB β α [PWAG α γ φq]))

16. Example (REQUEST sanjeev audience registered_for_AAAI_yesterday e raise_hand sanjeev_is_curious t ) Distributive reading

17. Example (cont.) (Goal sanjeev z.(registered_for_AAAI_yesterday z)  [ (DONE z raise_hand) Λ [PWAG z sanjeev (DONE z raise_hand) sanjeev_is_curious] ] ) “Whoever” registered for AAAI yesterday raise their hands and have a PWAG with me that they raise their hands. Note: the I need not know who all registered for AAAI yesterday when I made my request.

18. Meeting the constraints • Actor constraint -- βneed not equalγ • Sender awareness – quantifiers implicit in β not quantified into α • Actor awareness – quantifiers implicit in γ not quantified into α (for remaining constraints, see paper) Thus, a request can be made even if the sender does not know who the actor(s) γ or recipientsβ are -- nowhere are the quantifiers implicit in γ or β quantified into α

19. Requesting (REQUEST α β γ e a q t)  (ATTEMPT α eφψ t) Where β = recipient(s) γ = actor(s) α = sender(s) φ = ‹z (DONE γza) Λ[PWAG γz α (DONE γza) (PWAG α γ ‹w DONE γwa› q)] ›and ψ = [BMB β α (BEFORE e [GOAL α (AFTER e [PWAG α γ φq] )] )] Note: no superscript

20. FIPA ACL • FIPA (Foundation for Intelligent Physical Agents) • Agent communication • Agent management • Agent transport • Agent Communication Language (ACL) http://www.fipa.org/repository/aclspecs.html • Message structure • Interaction Protocols • Communicative Acts • Content Languages

21. FIPA Message • Performative (Communicative Act) • sender • receiver • reply-to • content • (content) language • (content) encoding • ontology • protocol • conversation-id • reply-with • in-reply-to • reply-by

22. FIPA Performatives • http://www.fipa.org/specs/fipa00037/SC00037J.html

23. FIPA Interaction Protocols • http://www.fipa.org/repository/ips.php3

24. KQML • Knowledge Query and Manipulation Language http://www.cs.umbc.edu/kqml/kqmlspec/spec.html http://www.csee.umbc.edu/~jklabrou/publications/ijcai97.pdf