Virtual Organizations as Normative Multiagent Systems Guido Boella Università di Torino, Joris Hulstijn Vrije Universiteit, Amsterdam, Leendert van der Torre CWI, Amsterdam,

HICSS'05Boella, Hulstijn, van der Torre2 Virtual Organizations Virtual Organizations: individuals and institutions that need to coordinate resources and services across institutional boundaries (Foster et al) Infrastructures: e.g. GRID, CSCW, KM, … Users form a virtual community, with shared norms and objectives. Align community norms with infrastructure rules? –Client-server: global policies, but no local control –Peer-to-peer: local control, but no global policies Need a conceptual model of norms at different levels of control.

HICSS'05Boella, Hulstijn, van der Torre3 Normative Multiagent Systems Normative system: set of norms (obligations) with an enforcement mechanism. Multiagent system: set of autonomous agents with beliefs, goals, actions... Model interaction between agents by recursive modeling Model normative system N as any other agent [Boella & Van der Torre KR’04,AAMAS’04]

HICSS'05Boella, Hulstijn, van der Torre4 Overview (i). Example (ii). NMAS (iii). Conclusions 1.How can the behavior of an individual agent in a virtual organization be described? 2.How can agents change a virtual organization? 3.How can agents in a virtual organization establish normative relations or contracts with each other? 4.How can we deal with norms that operate at different levels of control?

(i). Example

HICSS'05Boella, Hulstijn, van der Torre6 Distributed Access Control Global norms, but local access control. –owners have the right to entitle access to a resource –storage providers can grant or withhold access [Firozabadi and Sergot 2002] So a 2 must –check ID a 1, –check entitlement a 1 –weigh obligations against own goals userstorage provider owner entitle access request access ? a1a1 a2a2 a3a3

HICSS'05Boella, Hulstijn, van der Torre7 Observations Dynamic: agents can enter, leave and alter the normative system. Interactive: agents can agree on a contract (set of mutual obligations), enforced by N. Obligations are effective only when accompanied by an enforcement mechanism. Violation detection and sanctioning can be delegated to other agents. Roles: subjects, defenders, normative system

(ii). NMAS

HICSS'05Boella, Hulstijn, van der Torre9 Individual Agent Focus on goal generation Use sets of production rules P  Q to represent beliefs and goals, with a priority order <. Belief rules: information about current state Goal rules: information about ideal future state < Beliefs Goals Observations Actions Goals Goal Generation Planning & Scheduling

HICSS'05Boella, Hulstijn, van der Torre10 Example 1. Belief: at party 2. Goal: at party  drink beer 3. Goal: drink beer  smoke cigarette 4. Goal: ¬ smoke cigarette Priority: 1 > { 2, 4 } > 3 Outcome: { at party, drink beer, ¬ smoke cigarette },

HICSS'05Boella, Hulstijn, van der Torre11 Recursive Modeling Profile (set of P  Q rules) depends on role. Used for trust and deception. agent A deliberates about optimal decision – considers optimal decision of agent B agent B deliberates about optimal decision – considers optimal decision of agent A agent A deliberates about optimal decision – considers optimal decision of agent B

HICSS'05Boella, Hulstijn, van der Torre12 Constitutive Rules Establish institutional facts by constitutive rules [Searle 1995]. E.g. counts as an entitlement to lunch, at the HICSS conference. “P counts as Q in institutional context C” whenever C  P  Q is a belief of N Joris Hulstijn Thursday January 6, lunch ticket

HICSS'05Boella, Hulstijn, van der Torre13 Norms Obligation of A to N to bring about P in context C, under sanction S iff 1. Goal of N: C  P 2. Goal of N: (C  ¬P)  Viol(A, ¬P) 3. Goal of N: ¬ Viol(A, ¬ P) 4. Goal of N: Viol(A, ¬ P)  S 5. Goal of N: ¬ S 6. Goal of A: ¬ S 7. Goal of A: ¬P A: 6 > 7, N: 2 > 3, 4 > 5 My wish is your command?

HICSS'05Boella, Hulstijn, van der Torre14 Dynamics The fact that normative rules 1-6 hold, is itself an institutional fact, i.e. a belief of N. A performative speech act counts as the creation of an institutional fact in context C, provided … –preparatory conditions hold, and –sincerity, propositional and essential conditions hold. Owner a entitles b access to d, means either 1. create an obligation for all to grant b access to d, or 2. create a credential, used with a general access obligation.

(iii). Conclusions

HICSS'05Boella, Hulstijn, van der Torre16 Four kinds of Structures A regards N - e.g. decide to violate or not N regards A’s behavior - e.g. decide how to enforce A 1 regards A 2 given N - e.g. decide whether to trust N 1 regards N 2, given A’s behavior given N - e.g. decide to delegate or not A : N AN N : A AN N : N AN A : A AN

HICSS'05Boella, Hulstijn, van der Torre17 Conclusions Virtual organizations as normative multiagent systems. 1.Individual agents are modeled goal generation, based on beliefs, goals and priorities. 2.Dynamics can be captured by constitutive rules. 3.Using recursive modeling and interaction, complex normative relations can be broken down into four types: A:N, N:A, A:A (N) and N:N (A). 4.Norms at different levels of control, can be dealt with by delegation to embedded normative multiagent systems, leading to different roles: subjects, defenders and the normative system.

HICSS'05Boella, Hulstijn, van der Torre18 References G. Boella and L. van der Torre. Regulative and constitutive norms in normative multiagent systems. KR’04. G. Boella and L. van der Torre. Attributing mental attitudes to normative systems. AAMAS’04. J. R. Searle. The Construction of Social Reality. The Free Press, New York, Ronald M. Lee. Bureaucracies as deontic systems. ACM Transactions on Information Systems, 6(2):87 – 108, Jones, A.J.I. & Sergot, M.J. On the characterisation of law and computer systems In: Deontic Logic in Computer Science, Wiley 1993, L. Kagal, T. Finin, A. Joshi Trust-Based Security in Pervasive Computing Environments, Communication of the IEEE, 34 (12), 154 – 157, 2001

HICSS'05Boella, Hulstijn, van der Torre19 Distributed Access Control (2) 1.Goal of N: req(a 3,d)  cred(a 1,a 3,d)  acc(a 2,a 3,d) 2.Goal of N: req(a 3,d)  cred(a 1,a 3,d)  ¬ acc(a 2,a 3,d)  Viol(a 2, ¬ acc(a 2,a 3,d)) Goal of N: ¬ Viol(a 2, ¬ acc(a 2,a 3,d)) Goal of N: Viol(a 2, ¬ acc(a 2,a 3,d))  ban(a 2 ) Goal of N: ¬ ban(a 2 ) Goal of a 2 : ¬ ban(a 2 ) Goal of a 2 : ¬ acc(a 2,a 3,d) for a 2: 6 > 7 for N: 2 > 3, 4 > 5 userstorage provider owner entitle access request access ? a1a1 a2a2 a3a3

HICSS'05Boella, Hulstijn, van der Torre20 Example Obligation of a to n not to overfish in spring, under sanction of paying a fine. 1.Goal of n: spring  ¬ overfish Goal of n: spring  overfish  Viol(overfish, a) Goal of n: ¬ Viol(overfish, a) Goal of n: spring  Viol(overfish, a)  fine Goal of n: ¬ fine Goal of a: ¬ fine Belief of a,n: spring Goal of a: overfish Works only in case Desire 8 < Desire 6