1. Institutional Social Dynamic Dependence Networks Serena Villata University of Turin

2. S. Villata - Institutional Social Dynamic Dependence Networks 2 Social Network Theory Key technique in sociology, organizational studies and economics. Connotation of complex sets of relationships among the members of social systems. Social network: social structure composed by nodes (individuals or organizations) and edges (relationships among individuals) that form a complex structure.

3. S. Villata - Institutional Social Dynamic Dependence Networks 3 Normative MAS The presence of different types of entities with different capabilities inside the social network underlines the necessity of introducing social regulations. Relation between agent theory and social sciences such as sociology, philosophy, etc… Multiagent system research and sociology share the interest in the relation between micro-level agent behaviour and macro- level system effects.

4. S. Villata - Institutional Social Dynamic Dependence Networks 4 Power and Norms Agents are heterogeneous, cooperative and have different abilities. When an agent is not self-sufficient with respect to some goal, he can resort to some other agent, given that the latter cannot be self-sufficient itself in every respect. The aim of a normative MAS is regulating the behaviour of its agents thanks to norms and the institutional power that allows the introduction of new dependencies.

5. S. Villata - Institutional Social Dynamic Dependence Networks 5 Research Questions How to extend dependence networks to build social dependence networks which are able to model the dynamics of an institution? How to map the Institutional view of a multiagent system into the dynamic social network representation of it?

6. S. Villata - Institutional Social Dynamic Dependence Networks 6 The hypotetical Government Roles: Prime Minister and other ministries. Material services to work: ministerial car, press statement, service of translation, etc… Institutional services: authorizations, delegations, etc…

7. S. Villata - Institutional Social Dynamic Dependence Networks 7 Agent View Where - goals: relates with each agent the set of goals it is interested in. - skills: describes the actions each agent can perform. - rules: relates sets of actions with the sets of goals they see to.

8. S. Villata - Institutional Social Dynamic Dependence Networks 8 Institutional View Plurality of actors → necessity of introducing institutions and social regulations.Plurality of actors → necessity of introducing institutions and social regulations. Not only obligations and permissions but also institutional powers: ability to change institutional reality.Not only obligations and permissions but also institutional powers: ability to change institutional reality. Social institutions exist thanks to the collective acceptance of the institutional power.Social institutions exist thanks to the collective acceptance of the institutional power. Changes only according to its rules.Changes only according to its rules.

9. S. Villata - Institutional Social Dynamic Dependence Networks 9 The Institutional Reality Phisical reality associated to each agent, describing his beliefs, goals and capabilities.Phisical reality associated to each agent, describing his beliefs, goals and capabilities. The institution establishes a new level of reality in the relationships between involved actors that are associated to roles.The institution establishes a new level of reality in the relationships between involved actors that are associated to roles. This reality can be defined as the public or institutional reality.This reality can be defined as the public or institutional reality. This reality is associated to institutional goals, beliefs and capabilities: public character and change only according to accepted rules.This reality is associated to institutional goals, beliefs and capabilities: public character and change only according to accepted rules.

10. S. Villata - Institutional Social Dynamic Dependence Networks 10 Social Networks and Dependence Networks Social networks formalized as dependence networks. Social networks to study the relationships among the agents composing a MAS and the dynamics that arise from the interaction of these agents, modeling all by means of institutions. Multiagent systems give to social network theory new conceptual instruments as dependence networks. How to extend dependence networks to model institutional reality?

11. S. Villata - Institutional Social Dynamic Dependence Networks 11 Overview Power → capability of a group of agents to achieve goals. Dependence → possibility of a group Q of agents to satisfy goals of agents S. Institutional view → second level of reality. Institutional dependence network → abstract representation of the two levels.

12. S. Villata - Institutional Social Dynamic Dependence Networks 12 Agent’s Power Power is the capability of a group of agents to achieve some goals (theirs or of other agents) performing some actions without the possibility to be obstructed.

13. S. Villata - Institutional Social Dynamic Dependence Networks 13 Social Dependence Networks Agent described by a set of prioritized goals. Global dependence relation that explicates how an agent depends on the other agents for fulfilling its goals. –dep: 2 A x 2 A → 2 2 G -> relates with each pair of sets of agents all the sets of goals on which the first depends on the second. –≥: A → 2 G x 2 G

14. S. Villata - Institutional Social Dynamic Dependence Networks 14 Example of Social Dependence Network T K L P J I F g1 g2 g5 g3 g4 g8 g6 g7 g5

15. S. Villata - Institutional Social Dynamic Dependence Networks 15 Institutional View Where and igoals: relates with each role the set of public goals it is committed to. iskills: describes the institutional actions each role can perform. irules: relates sets of institutional actions with the sets of institutional facts they see to.

16. S. Villata - Institutional Social Dynamic Dependence Networks 16 Dynamics of Institutional view In the material world, no elements can be added dynamically to the agents’ facts, skills and goals, since agents are autonomous by definition. In contrast, the institutional view can be changed in all its aspects since it is publicly attributed to agents by collective acceptance according to the constitutive rules of the institution. Institutional powers allow to change the structure of the institutional view, and thus, changing the powers of roles agents play, it consequently changes the structure of the social dependence network.

17. S. Villata - Institutional Social Dynamic Dependence Networks 17 Social Dynamic Dependence Networks (DDN) Property needed for the institution: the possibility to change the institution according to the constitutive rules it specifies by itself. –ddep: 2 A x 2 A x 2 A → 2 2 G relates with each triple of sets of agents all the sets of goals on which the first depends on the second if the third creates the dependency. –≥: A → 2 G x 2 G

18. S. Villata - Institutional Social Dynamic Dependence Networks 18 Example of Institutional view RL –Minister of Finance (Fm), Prime Minister (Pm), Minister of Transport (Tm), Minister of Public Works (Wm) and Minister of Infrastructures (Im); RG –To obtain the authorization to built the bridge of Messina, to obtain fundings to start a new series of public works in the major cities of Italy, to not be present to a council of ministers because of family problems. IX –Authorize to built the bridge of Messina, authorize fundings to start a new series of public works in the major cities of Italy, give a delegation to minister Fm to give justification of absence. IF –Authorization to built the bridge of Messina, legislative powers to role Pm ad interim, approved absence of role Wm.

19. S. Villata - Institutional Social Dynamic Dependence Networks 19 Example of Institutional view RL = {Pm, Fm, Tm, Wm, Im}; RG = {pg1, pg2, pg3, pg4, pg5, pg6, pgN}; IX = {ixa, ixb, ixc, ixd, ixe, ixf, ixg, ixN}; IF = {ifa, ifb, ifc, ifd, ife, iff, ifN}; roles (Fm) = {F}, roles (Pm) = {P}, roles (Tm) = {T}, roles (Wm) = {L}, roles(Im) = {I}; igoals (Fm) = {pg6}, igoals (Pm) = {pg5}, igoals (Tm) = {pg1}, igoals (Wm) = {pg2, pg3, pg4}, igoals (Im) = {pg5}; iskills (Fm) = {ixb, ixd, ixe, ixg, ixN}, skills (Pm) = {ixc, ixd, ixf }, skills (Tm) = {ixg}, iskills (Wm) = {ixg}, iskills (Im) = {ixa, ixg} irules ({ixa}) = {ifb}, irules ({ixb}) = {ifc}, irules ({ixc}) = {ife}, irules ({ixd}) = {ifa}, irules ({ixe}) = {ifd}, irules ({ixf }) = {ife}, irules({ixg}) = {iff }, irules({ixN}) = {ifN};

20. S. Villata - Institutional Social Dynamic Dependence Networks 20 DDN T K L P J I F g1 g2 g5 g3 g4 g8 g6 g7 g5 g4 g8 Agent I with role Im has a bad behaviour, he is under investigation for corruption! Thus, the Prime Minister deletes the power of role Im to authorize fundings for a call for tenders for the bridge of Messina The Prime Minister takes ad interim the power of role Im.

21. S. Villata - Institutional Social Dynamic Dependence Networks 21 Conclusions Institutional powers applied to social networks.Institutional powers applied to social networks. Institutional social network is a social network that represents set of individuals regulated by institutional powers and with the application of social roles.Institutional social network is a social network that represents set of individuals regulated by institutional powers and with the application of social roles. A dynamic social dependence network represents various static social networks, by putting two networks into a single dynamic social dependence network.

22. S. Villata - Institutional Social Dynamic Dependence Networks 22 Future Work Definition of measures like social importance in dynamic dependence networks. Identification of coalitions inside a social dependence network. Definition of the concept of stability of a coalition, relating it to coalition’s dynamics. Extension to obligations and permissions.

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