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Towards a Simulation Tool for Towards a Simulation Tool for Evaluating Dynamic Evaluating Dynamic
Reorganization of Agent Reorganization of Agent SocietiesSocieties
V. Dignum, F. Dignum, Utrecht UniversityL. Sonenberg, University of MelbourneV. Furtado, A. Mello, University of Fortaleza
OutlineOutline
Main issues Motivation Organizations and change Reorganization typology Reorganization requirements The VILLA simulation environment Conclusions
Main issues in Main issues in ReorganizationReorganization
1. When2. Why 3. What
• Behavior• Structure
4. Who5. How
• External to system: re-design• Within system: dynamic
– Decision, authority
MotivationMotivation
Need for organization– Stability– Cope with uncertainty
Need for reorganization– Answer to change
• environment, objectives, population
– Flexibility
Need for reorganizationNeed for reorganization
Need for organization: achieve stability
Reorganization means loss of stability Need for reorganization
– Answer to environment changes– Answer to population changes– Answer to objective changes
Reorganization decision depends on – organizational utility and success.– individual utility and success
Organizational UtilityOrganizational Utility
Organizational Success: ability to bring assets to bear, recognize and take advantage of opportunities.– Ex: MAS perspective
• Interaction success: how often result in desired aim?• Role success: how often agents achieve role goals?• Structure success: how well are global goals
achieved?• Combined utilities of agents in organization
Utility: determined based on– Current success – Expected success– Cost of reorganization
Individual UtilityIndividual Utility
Success and utility are different for each agent– Dependent on own goals and
resources– Dependent on social attitude
Role utility to agent success determines participation in organization
Moments of reorganization – Moments of reorganization – when and why?when and why?
From organizational theory Timing (timeliness)
– Proactive: prepare for expected change
– Reactive: adjust after change Intention (resiliency)
– Offensive: gain advantage– Defensive: ensure survival
[Evans, 1991]
Reorganization manouvresReorganization manouvres
Intention
Tim
ing
pre-emptive-Expected future-Competition through innovation
offensive defensive
react
ive
pro
act
ive
protective-Expected future-Limit damages
exploitive-Taken after event-Capitalize opportunities
corrective-Taken after event-Prevent more damage-Ensure continuity
Focus of Reorganization – Focus of Reorganization – what?what?
Behavior change– Temporary, ‘local’ to one population– A new agent joins the MAS– An agent leaves the MAS– Interaction pattern instantiation
Structural change– Permanent, valid across populations– Organizational Self Design– Structural Adaptation
Means for reorganization – Means for reorganization – how?how?
Decision– concerns how reorganization
decisions are reached.– Relates to the decision-making style.
Authority– Concerns what aspects can be
changed by who in the organization– Relates to the C2 Model
Reorganization Decision – Reorganization Decision – who?who?
Externally imposed– Agents have no influence on reorganization – occurs through system redesign
Role based– Command-driven: the agent does not make any
decisions on how to pursue its goals, and some other agent has authority over it
– Locally autonomous/master: The agent makes decisions alone and may or not have control over other agents
True consensus – Agent works as a team member, sharing decision
making control equally with other agents
[Barber, Martin, 2001]
Reorganization Authority – Reorganization Authority – what?what?
C2 Model– Command: authority and responsibility to
determine the objectives of the organization. Can update the social structure of the organization.
– Control: authority to specify and modify detailed plans for achieving objectives. Authority to modify interactions and behavior.
C3 Model: C2 plus– Communications: collection and sharing
information about the environment, the state of the organization, the state of the achievement of objectives, and the state of execution of the plans.
• Meta-communication [Galey, 1987, Tidhar, Sonenberg, 2001]
Dynamic reorganization Dynamic reorganization stylesstyles
Authority
Deci
sion
Shared control
Shared command
Role-basedcontrol
Role-basedcommand
Behavior Structure
dir
ect
ive
colla
bora
tive
Requirements for Requirements for reorganizationreorganization
Observation– Identify patterns– Evaluate current response
possibilities– Generate options, predict outcomes,
understand effects Organizational requirements Agent capabilities
Organizational Organizational requirementsrequirements
Reorganization success– Timeliness– Adaptance/consensus– Resiliency
Depend on organizational form/domain– Hierarchy: role-based reorganization
decision?– Network: shared reorganization decision?– Market: favors behavior change?
Agent capabilitiesAgent capabilities
Authority
Deci
sion
Shared Control• no memory• reasoning• meta-communication
Behavior Structure
dir
ect
ive
colla
bora
tive
Shared Command• memory• reasoning• meta-communication
Role-based control• no memory• reasoning: only role• no meta-communic.
Role-based Command
• memory: only role• reasoning: only role• no meta-communic.
Simulation Aims - 1Simulation Aims - 1
Full theory of reorganization is more than what can be studied in one simulation
Agent behavior depends on– Own state and environment state– But also on the organizational structure– Organizational structure is thus not just a
component of the environment Organizational elements considered:
– Type of goal (simple to complex)– Roles (many agents, one agent)– Interactions (communication protocols, dole
dependencies)
Simulation Aims - 2Simulation Aims - 2
1. Identify match of organization structure to environment characteristics
2. Adaptation to (drastic) changes– Structural vs. behavioral– Role-directed vs. collaborative
3. Communication requirements to reason about change
– Also, reasoning with limited knowledge
The VILLA environmentThe VILLA environment
Aim: community survival Creatures
– Gatherers: can collect (limited) food individually
– Hunters: can hunt (large amounts of) food in groups
– Others: consume food, can grow to become Gatherers or Hunters
– Head: observe and change society
VILLA: ActivitiesVILLA: Activities
Simulation takes a number of runs (days)
In each run:– Eat
• If food available• Collectors eat more than others• If not eat, health decreases• If health = 0, then creature dies
– Collect• Gatherers: individual function on health• Hunters: groups’ function on health and size
– Move• Hunters must move to form group
VILLA setupVILLA setup
VILLA without VILLA without reorganizationreorganization
Evaluation of VILLAEvaluation of VILLA
Influences on health:– Role typology– Role capabilities
Results from evaluation of non reorganization situation:– Food stack decreases a lot at beginning– Need to introduce delay in adaptation– Others average health seems to be good
indicator for reorganization– Need to evaluate time interval, not time
point
Evaluation of VILLA (no Evaluation of VILLA (no reorg)reorg)
G H O Comments17 0 0 Gatherers survive with 100% of health. 6 11 0 All creatures die because amount of food is not sufficient to keep a
good health level. 0 9 8 All creatures die. Only in cases when the hunters get together very
early some creatures survive. Hunters keep others alive if food stack is very high (more than 10000)
0 17 0 All creatures survive more than 100 TICs. However, food stack must be 900 to allow Hunters to get together within 500 ticks.
9 8 0 Very good society but depends on the probability of Hunters to get together.
8 5 4 Stable society with health 80%. However some Others will die.8 6 3 Stable society with health 80%. However some Others will die.8 6 2 Good and stable society with health greater than 80%7 5 4 All creatures die7 7 3 All creatures die7 3 7 All creatures die9 5 3 Very good society9 6 2 Good society9 7 1 Very good society with health 95% but instable if Hunters are isolated.6 10 1 Very good society with health in 95% but instable if Hunters are
isolated.5 11 1 Very good society with health in 95% but instable if Hunters are
isolated.4 11 2 Good society but very instable if Hunters are isolated.3 11 3 Good society but very instable if Hunters are isolated.
Evaluation of VILLA (no Evaluation of VILLA (no reorg)reorg)
G H O Prob. Gather
Prob. Hunter
Comments
9 5 3 9 10 Instable Society, depending on hunters’ aggregation.
9 6 2 9 10 Instable Society, depending on hunters’ aggregation.
9 5 3 15 18 Stable society independent of hunters aggregation. Reach 100% and food stack increase.
9 6 2 15 18 Stable society independent of hunters aggregation. Reach 100% and food stack increase.
9 0 8 15 18 Stable society independent of hunters aggregation. Reach 100% and food stack increase.
5 0 12 15 18 Minimum number of gatherers for supporting other life.
0 17 0 15 18 With the increasing of prob. Hunters always still alive and keep society good
8 5 4 15 18 Health society before was 80% now 100%.
7 7 3 15 18 Stable society independent of hunters aggregation. Reach 100% and food stack increase.
7 6 4 15 18 100% “
7 5 5 15 18 100% ”
7 5 5 18 20 100%
Reorganizing SocietiesReorganizing Societies Behavioral change:
– If food stack < 250, increase gather power by 1
– Reorganization delay is 100
Reorganizing SocietiesReorganizing Societies Structural change:
– If food stack < 250, create 1 gatherer (from Others)
– Reorganization delay is 100
ConclusionsConclusions
First step towards a model of reorganization
Identification of characteristics of reorganization
Requirements for reorganization– Different organizational types– Challenges for agent capabilities
Future workFuture work
Empirical study – How systems react to different
reorganization forms– Further evaluation/development of VILLA
Reorganization methodology– Conditions and requirements– Determine choices
Formal model for reorganization? – Organizational utility– Reorganization cost