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Using social power to enable agents to reason about being part of a group

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Using social power to enableagents to reason about beingpart of a group

C.Carabelea, O.Boissier, C.Castelfranchi

- Autonomous agents have control over their local behaviour.
- One of the main challenges in multi-agent systems is the coordination of autonomous agents.
- Bottom-up, emergent, coordination, usually based on
- a model of relationships between goals, plans, etc. (e.g., TAEMS)
- a reasoning about the dependencies between agents

- Top-down coordination, usually based on:
- organizational structures
- norms, contracts
- institutions

Powers and groups

- Our aim is not to engineer societies, but to engineer agents to understand societies.
- We want to propose an unified model of reasoning about the constraints imposed by the coordination with other agents in both institutional and non-institutional contexts.
- We will base this model on the social power theory:
- social sciences’ theory describing the powers an agent has individually or with respect to other agents
- informal, it needs to be formalized in order to enable agents to use it

- The formalization presented in this paper is still an ongoing work

Powers and groups

- The powers of an agent
- individual powers: executional, deontic, etc.
- social powers: dependence and influencing power
- institutional powers: due to authorities, norms and contracts

- Using powers to reason about being part of a group
- Other utilisations of the power theory
- operations with power
- agent autonomy
- punishments and rewards

- Conclusions and future work

Powers and groups

- We tried to keep our model as general as possible and not related to a specific model of agency or to a specific institutional model.
- We describe the agents’ behaviour in terms of:
- actions that need resources in order to be executed
- goals achieved using plans formed by actions, resources and sub-goals

- We use a number of predefined predicates that make the connection with existing, complementary, models (e.g., BDI):
- has(X, resource), knows_how(X, action), goal(X, goal)
- allowed_to(X, ...), can_empower(X, Y, ...)

Powers and groups

- Executional power: can_do
can_do(X, Res) =d has(X, Res)

can_do(X, Act) =d knows_how(X, Act) Ù(R needs(Act, R) can_do(X, R))

can_do(X, G) =d $plG achieves(plG, G) Ù can_do(X, plG)

can_do(X, plG)=d "a plG can_do(X, a), where a is an action, resource or subgoal

- Deontic power: entitled_to
similar with can_do, but using the predicate allowed_to

- Power of:
power_of(X, P) =d can_do(X, P) Ù entitled_to(X, P)

Powers and groups

resources

power_of

A

Powers and groups

- Agents depend on each other because they lack powers (Sichman et al.):
- executional:
depends_on(X, Y, G)=d plG achieves(plG, G)

plGØcan_do(X,) can_do(Y,)

- deontic:
depends_on(X, Y, G)=d Øentitled_to(X, G) can_empower(Y, X, G)

- executional:
- An agent has the power of influencing another agent due to a dependence:
X Y P power_of(X, P) Ù (G depends_on(X, Y, G) Ù goal(X, G))

dep_infl_power(Y, X, P)

Powers and groups

resources

power_of

dependence (Øentitled_to)

dep_infl_power

dependence (Øcan_do)

dep_infl_power

A

B

C

Powers and groups

- There are many forms of dependences (Sichman et al.):
- mutual, reciprocal, OR-dependencies, etc.

- Dependence-networks have been proposed as a mechanism for agent coordination, e.g., agents reason about dependencies to choose coordination partners.
- Top-down coordination models are based on different notions, like roles, hierarchies, norms, contracts, etc.
- We use the term group to denote anything in the range of institutions, organizations, normative societies, teams, etc.

Powers and groups

- Agents belong to groups:
belongs_to(X, Gr)

- A group can use the notion of contract between two agents:
contract(X, Y, P, Gr)

- We are not interested in how the group enforces the fulfillment of contracts (detection, punishments, etc.), but only that signing a contract in a group limits an agent’s behaviour:
X,Y Gr belongs_to(X, Gr) Ù belongs_to(X, Gr) Ù P contract(X, Y, P, Gr) contr_infl_power(Y, X, P)

Powers and groups

resources

Group Gr

power_of

contract

dependence (Øentitled_to)

contr_infl_power

dep_infl_power

dependence (Øcan_do)

dep_infl_power

A

D

B

C

Powers and groups

- In a group, the behaviour of agents is not limited only by the dependences or the contracts signed towards other agents.
- Agents play roles organized in hierarchies (authority relations):
plays_role(X, R, Gr), authority_over(Gr, R1, R2, P)

- Influencing power due to authority (organisational structure):
X,Y Gr R1,R2plays_role(X, R1, Gr) Ù plays_role(Y, R2, Gr) Ù

P authority_over(Gr, R2, R1, P) org_infl_power(Y, X, P)

Powers and groups

resources

Group Gr

R3

E

authority_over

power_of

org_infl_power

R1

contract

dependence (Øentitled_to)

contr_infl_power

dep_infl_power

dependence (Øcan_do)

org_infl_power

authority_over

dep_infl_power

R2

F

A

D

B

C

Powers and groups

- Norms have been used to regulate agents’ behaviour.
- There is still an ongoing work on their definition and formalization, but generally norms are considered to be of three types: obligations, permissions and interdictions.
- We use these predicates to define norms that target a role in a group and the object of these norms:
permission(Gr, R, P), interdiction(Gr, R, P), obligation(Gr, R, P)

- Influencing power due to a norm (an obligation):
X Gr R plays_role(X, R, Gr) Ù P obligation(Gr, R, P)

norm_infl_power(group, X, P)

Powers and groups

resources

Group Gr

R3

E

authority_over

power_of

org_infl_power

R1

contract

dependence (Øentitled_to)

contr_infl_power

dep_infl_power

obligation

dependence (Øcan_do)

org_infl_power

authority_over

dep_infl_power

norm_infl_power

R2

F

the group

A

D

B

C

Powers and groups

- The norms modify an agent’s deontic powers:
X Gr R plays_role(X, R, Gr) ÙP permission(Gr, R, P) allowed_to(X, P)

X Gr R plays_role(X, R, Gr) ÙP interdiction(Gr,R,P) Øallowed_to(X, P)

- allowed_to is the source of an agent’s deontic power (entitled_to), which in turn is a component of an agent’s power_of.
- Thus, by playing a role in a group an agent might increase its powers by receiving permissions, but also by receiving resources (e.g., money).

Powers and groups

resources

resources

Group Gr

R3

E

authority_over

power_of

power_of

org_infl_power

R1

contract

dependence (Øentitled_to)

contr_infl_power

dep_infl_power

obligation

dependence (Øcan_do)

org_infl_power

authority_over

dep_infl_power

norm_infl_power

R2

F

the group

A

D

B

C

Powers and groups

resources

resources

Group Gr

R3

E

authority_over

power_of

power_of

org_infl_power

R1

contract

contr_infl_power

obligation

dependence (Øcan_do)

org_infl_power

authority_over

dep_infl_power

norm_infl_power

R2

F

the group

A

D

B

C

Powers and groups

- When deciding whether to enter a group (e.g., an agent organization) or not (or to play a role or not), an agent can reason in terms of powers:
- what are the powers that it will gain or lose?
- who will be able to constrain its behaviour and why?
- will it be able to constrain other agents’ behaviour?
- what existing limitations of its behaviour are no longer valid?

- This only complements and not replaces classical decision-making:
- e.g. utility-based
- it still has to decide whether to disobey a norm or not (by taking into account the associated punishments, the probability of being caught, etc.)

Powers and groups

- The powers of an agent are dynamic:
- because of the dynamics of the environment or the actions of other agents’
- because of the changes in the society

- But there are also operations with powers that can be done by the agents:
- Transfer of power
- Putting at the disposal of an agent a power
- Empowerment – especially interesting in agent institutions
- Delegation / adoption – an agent adopting a goal from another agent implicitly gives it an indirect power to achieve that goal.

Powers and groups

- There are different types of autonomy in MAS: social autonomy, norm-autonomy, user-autonomy, etc.
- The term autonomy is used in related work with two different meanings
- Autonomy as independence (Castelfranchi)
dep_independence(X, Y, P)=dØ dep_infl_power(Y, X, P)

- Autonomy as the capacity of deciding about the adoption of a goal (Luck et al.)
X,Y P dep_infl_power(Y, X, P) Ù delegation(Y, X, P) ÙØadoption(X, Y, P)

dep_autonomous(X, Y, P)

- Autonomy as independence (Castelfranchi)
- Same definitions for the other types of autonomy: org-autonomy, norm-autonomy, contract-autonomy.

Powers and groups

- We can use autonomy to define coordination-enforcement mechanisms. For example, for organizational autonomy:
X,Y P org_infl_power(Y, X, P) Ù delegation(Y, X, P) ÙØadoption(X, Y, P)

org_autonomous(X, Y, P)

- Disobeying the hierarchy should be punished:
X Gr belongs_to(X, Gr) Ù Y P org_autonomous(X, Y, P)

is_punished(X, Gr, punishment)

- Non-mandatory cooperation is rewarded:
X Gr belongs_to(X, Gr) Ù Y P delegation(Y, X, P) Ù adoption(X, Y, P) Ù

Øorg_infl_power(Y, X, P) is_rewarded(X, Gr, reward)

Powers and groups

contr_autonomous

D

resources

resources

Group Gr

R3

E

authority_over

power_of

power_of

org_infl_power

R1

contract

contr_infl_power

punishment

obligation

dependence (Øcan_do)

org_infl_power

authority_over

dep_infl_power

norm_infl_power

R2

F

the group

A

D

B

C

Powers and groups

- Reasoning about powers complements classical reasoning, agents can use powers to understand the constraints they face in a group.
- An unified model of reasoning about constraints imposed by bottom-up (e.g., dependence-based) and top-down coordinations (e.g., organizations)
- Can be used to classify and define different types of autonomy.

Powers and groups

- The formalization we propose is quite simple because we tried to keep this model as general as possible.
- We intend to “tailor” our model (by defining key predicates like goal, norm, etc.) to existing coordination models in order to be able to endow agents with a power-based reasoning engine.
- e.g., use TAEMS for bottom-up and MOISE+ for top-down coordination.

- The same approach can be used to engineer institutions too.
- For this we must formally define operations with powers (especially institutional empowerment).

Powers and groups

resources

resources

Group Gr

R3

E

authority_over

power_of

power_of

org_infl_power

R1

contract

dependence (Øentitled_to)

contr_infl_power

dep_infl_power

obligation

dependence (Øcan_do)

org_infl_power

authority_over

dep_infl_power

norm_infl_power

R2

F

the group

A

D

B

C

Powers and groups