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Mechanisms to Promote Cooperation in Decentralized Services
Mechanisms to Promote Cooperation in Decentralized Services
Mechanisms to Promote Cooperation in Decentralized Services
Mechanisms to Promote Cooperation in Decentralized Services
Mechanisms to Promote Cooperation in Decentralized Services
Mechanisms to Promote Cooperation in Decentralized Services
Mechanisms to Promote Cooperation in Decentralized Services
Mechanisms to Promote Cooperation in Decentralized Services
Mechanisms to Promote Cooperation in Decentralized Services
Mechanisms to Promote Cooperation in Decentralized Services
Mechanisms to Promote Cooperation in Decentralized Services
Mechanisms to Promote Cooperation in Decentralized Services
Mechanisms to Promote Cooperation in Decentralized Services
Mechanisms to Promote Cooperation in Decentralized Services
Mechanisms to Promote Cooperation in Decentralized Services
Mechanisms to Promote Cooperation in Decentralized Services
Mechanisms to Promote Cooperation in Decentralized Services
Mechanisms to Promote Cooperation in Decentralized Services
Mechanisms to Promote Cooperation in Decentralized Services
Mechanisms to Promote Cooperation in Decentralized Services
Mechanisms to Promote Cooperation in Decentralized Services
Mechanisms to Promote Cooperation in Decentralized Services
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Mechanisms to Promote Cooperation in Decentralized Services

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  • 1. Outline System Model Cooperation Mechanisms Results Conclusions Mechanisms to promote cooperation in decentralized services E. del Val M. Rebollo V. Botti Univ. Politecnica de Valencia (Spain) EUMAS ’12 Dublin, December 2012M. Rebollo et al. (UPV) EUMAS’12Mechanisms to promote cooperation in decentralized services
  • 2. Outline System Model Cooperation Mechanisms Results ConclusionsPromoting Cooperation Motivation There are scenarios in decentralized systems in which cooperation plays a central role agents connected in networks bounded rationality heterogeneous, self-interested agentsM. Rebollo et al. (UPV) EUMAS’12Mechanisms to promote cooperation in decentralized services
  • 3. Outline System Model Cooperation Mechanisms Results ConclusionsOur Proposal The challenge Obtain an emergent, cooperative global behavior even when cooperators are a minority, from local decisions. What is done. . . a network structure that ensures navigation and efficiency structural changes to isolate undesired agents incentives to promote cooperationM. Rebollo et al. (UPV) EUMAS’12Mechanisms to promote cooperation in decentralized services
  • 4. Outline System Model Cooperation Mechanisms Results ConclusionsOutline 1 Outline 2 System Model 3 Cooperation Mechanisms 4 Results 5 ConclusionsM. Rebollo et al. (UPV) EUMAS’12Mechanisms to promote cooperation in decentralized services
  • 5. Outline System Model Cooperation Mechanisms Results ConclusionsSystem Model Definition (Open Service-Oriented MAS) (A, L), where A = {ai , ..., an } is a finite set of autonomous agents that are part of the system, and L ⊆ A × A is the set of links, where each link (ai , aj ) ∈ LM. Rebollo et al. (UPV) EUMAS’12Mechanisms to promote cooperation in decentralized services
  • 6. Outline System Model Cooperation Mechanisms Results ConclusionsSystem Model Definition (Agent) is a tuple (Si , Ni , sti ) where: Si = {s1 , . . . , sl } is the set of semantic service descriptions of the services provided by the agent (WSDL); Ni is the set of neighbors of the agent, Ni ⊆ A − {ai } : ∀aj ∈ Ni , ∃(ai , aj ) ∈ L, and |Ni | > 0. It is assumed that |Ni | |A|; sti is the internal state of the agent. πi : sti → Ni is the neighbor selection function that determines the most promising neighbor to provide a service; ρi : sti → Ψ is the adaptation selection function where Ψ is the set of finite adaptation actions of the agent.M. Rebollo et al. (UPV) EUMAS’12Mechanisms to promote cooperation in decentralized services
  • 7. Outline System Model Cooperation Mechanisms Results ConclusionsNetwork Creation probabilistic relations baed on homophily (assortativity, similarity) two agents are similar if they provide similar services H = αHv + (1 − α)Hs growing network structure (exponential degree distribution) certain characteristics of a small-world network (short paths, clustering)M. Rebollo et al. (UPV) EUMAS’12Mechanisms to promote cooperation in decentralized services
  • 8. Outline System Model Cooperation Mechanisms Results ConclusionsService Discovery navigation problem in networks (it relies in the agent cooperation) hill climbing (greedy) method    |Nj |       H(aj , at )   π(at ) = argmax 1 − 1 −        H(an , at )    aj ∈Ni    an ∈Ni agents pass the query until the desire service is found it is a problem with self–interested agentsM. Rebollo et al. (UPV) EUMAS’12Mechanisms to promote cooperation in decentralized services
  • 9. Outline System Model Cooperation Mechanisms Results ConclusionsSocial Plasticity capacity to change relations as times passes link utility decays with time depends on the queries aj forwards 1 D(aj ) = 1+e −γM. Rebollo et al. (UPV) EUMAS’12Mechanisms to promote cooperation in decentralized services
  • 10. Outline System Model Cooperation Mechanisms Results ConclusionsSocial Plasticity when an agent breaks a link, a substitute must be found (maintain the network structure) criteria neighbor of neighbor a similar agent to the previous one rewire links has not a costM. Rebollo et al. (UPV) EUMAS’12Mechanisms to promote cooperation in decentralized services
  • 11. Outline System Model Cooperation Mechanisms Results ConclusionsSocial PlasticityM. Rebollo et al. (UPV) EUMAS’12Mechanisms to promote cooperation in decentralized services
  • 12. Outline System Model Cooperation Mechanisms Results ConclusionsSocial PlasticityM. Rebollo et al. (UPV) EUMAS’12Mechanisms to promote cooperation in decentralized services
  • 13. Outline System Model Cooperation Mechanisms Results ConclusionsIncentives each action implies a cost (ask for a service and forward) a reward is obtained if the service is found rewards are provided by the system agents imitated the strategy of successful neighborsM. Rebollo et al. (UPV) EUMAS’12Mechanisms to promote cooperation in decentralized services
  • 14. Outline System Model Cooperation Mechanisms Results ConclusionsIncentivesM. Rebollo et al. (UPV) EUMAS’12Mechanisms to promote cooperation in decentralized services
  • 15. Outline System Model Cooperation Mechanisms Results ConclusionsCombining social plasticity and incentives Both strategies promote cooperation in general but it is not enough if non–cooperative agents has a high degree network broken in isolated parts rewire cost –> not affordable for some agents payoff not enough to promote cooperation the combined model 1 incentives to change the behavior of non–cooperatives 2 rewire links if it failsM. Rebollo et al. (UPV) EUMAS’12Mechanisms to promote cooperation in decentralized services
  • 16. Outline System Model Cooperation Mechanisms Results ConclusionsExperiment Design Configuration 1,000 agents, 10 different networks 100 steps to forward a query, snapshots after 5,000 queries varying the initial prop. of collaborators Strategies Social plasticity (SP) Incentives Reinforcement Learning (RL) using WOLF Game-theory approach, using Prisoner’s Dilemma (PD) Incentives + Social Plasticity (I+SP)M. Rebollo et al. (UPV) EUMAS’12Mechanisms to promote cooperation in decentralized services
  • 17. Outline System Model Cooperation Mechanisms Results ConclusionsMeasures proportion of collaborator / non–collaborators average path length (better if smaller) search failures due to non–collaboration search success (including TTL)M. Rebollo et al. (UPV) EUMAS’12Mechanisms to promote cooperation in decentralized services
  • 18. Outline System Model Cooperation Mechanisms Results Conclusions60% of collaborators (num and path length)M. Rebollo et al. (UPV) EUMAS’12Mechanisms to promote cooperation in decentralized services
  • 19. Outline System Model Cooperation Mechanisms Results Conclusions40% of collaborators (num and path length)M. Rebollo et al. (UPV) EUMAS’12Mechanisms to promote cooperation in decentralized services
  • 20. Outline System Model Cooperation Mechanisms Results Conclusions60% of collaborators (failures and success)M. Rebollo et al. (UPV) EUMAS’12Mechanisms to promote cooperation in decentralized services
  • 21. Outline System Model Cooperation Mechanisms Results Conclusions40% of collaborators (failures and success)M. Rebollo et al. (UPV) EUMAS’12Mechanisms to promote cooperation in decentralized services
  • 22. Outline System Model Cooperation Mechanisms Results ConclusionsConclusions improving cooperation to solve navigation problem in networks applied to decentralized service management combination of structural changes and incentives improves the performance when non-collaborators are ’important’ in the network works by imitation: a core of collaborators is needed a guess: the size of the core depends on network characteristics (percolation, efficience, centrality coefficient)M. Rebollo et al. (UPV) EUMAS’12Mechanisms to promote cooperation in decentralized services

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