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Self-Organized Service Management in Heterogeneous and Dynamic MAS
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Self-Organized Service Management in Heterogeneous and Dynamic MAS

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  • 1. Outline System Definition Homophily-based Network Adaption Process Discussion Conclusions Self–Organized Service Management in Heterogeneous and Dynamic MAS M. Rebollo, E. del Val and V. Botti Univ. Politecnica de Valencia (Spain) 9th European Workshop on Multi-Agent Systems Maastricht, November 2011@mrebollo UPVSelf–Organized Service Management in Heterogeneous and Dynamic MAS
  • 2. Outline System Definition Homophily-based Network Adaption Process Discussion ConclusionsSelf–Organized Service Management The Problem Automatic service self-adaption to the system demand without global knowledge ! Ag12 Ag20 ! ! ! dg=1 Ag11 dg=1 Sl ! Sk ! Ag20 ! ! dg=3 Sh dg=1 Ag17 Ag13 Ag2 Sk ! ! ! ! ! ! dg=1 dg=1 dg=4 Sh Sk Sk Ag19 ! ! Ag14 ! Ag3 ! Ag16 ! Ag8 ! ! Ag1 dg=1 Sm ! dg=2 ! dg=2 ! ! Sp Sc ! Ag9 dg=3 dg=4 ! Sj dg=2 Ag18 So ! Ag4 Sa ! dg=1 Ag7 ! ! Ag15 Sj ! ! dg=2 ! ! dg=3 Sm ! Sd Ag10 dg=2 Si dg=1 Sp ! Ag5 ! ! ! dg=1 Si Ag6 ! dg=2 Sb ! dg=2 Sf@mrebollo UPVSelf–Organized Service Management in Heterogeneous and Dynamic MAS
  • 3. Outline System Definition Homophily-based Network Adaption Process Discussion ConclusionsOur Proposal The challenge The introduction of the homophily concept improves the performance of greedy local search algorithms and it can be used as individual adaption criteria. What is needed. . . a network structure with small world characteristics an efficient search algorithm an adaptation mechanism to fit to the service demand@mrebollo UPVSelf–Organized Service Management in Heterogeneous and Dynamic MAS
  • 4. Outline System Definition Homophily-based Network Adaption Process Discussion ConclusionsOutline 1 Outline 2 System Definition 3 Homophily-based Network 4 Structural Homophily as Local Self-Adaptive Method 5 Discussion 6 Conclusions@mrebollo UPVSelf–Organized Service Management in Heterogeneous and Dynamic MAS
  • 5. Outline System Definition Homophily-based Network Adaption Process Discussion ConclusionsSystem DefinitionHomophily based network Homophily Tendency of individuals to associate and interact with similar ones choice homophily: similarity measure value homophily: shared attributes status homophily: role structural homophily: adaption to external conditions@mrebollo UPVSelf–Organized Service Management in Heterogeneous and Dynamic MAS
  • 6. Outline System Definition Homophily-based Network Adaption Process Discussion ConclusionsSystem DefinitionNetwork Model Definition (System model) (A, L), where A = {a1 , ..., an } is a finite set of autonomous agents and L ⊆ A × A is the set of links, where each link (ai , aj ) ∈ L indicates the existence of a direct relationship between agent ai and aj .@mrebollo UPVSelf–Organized Service Management in Heterogeneous and Dynamic MAS
  • 7. Outline System Definition Homophily-based Network Adaption Process Discussion ConclusionsSystem DefinitionNetwork Model Definition (Agent) An agent ai ∈ A = (Ri , Ni , sti , πi , ρi ), where: Ri = {r1 , . . . , rm } is the set of roles played by the agent; Ni is the set of neighbors of the agent, Ni = {ap , ..., aq } : ∀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 returns 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.@mrebollo UPVSelf–Organized Service Management in Heterogeneous and Dynamic MAS
  • 8. Outline System Definition Homophily-based Network Adaption Process Discussion ConclusionsSystem DefinitionNetwork Model Definition (Role model) A role ri ∈ Ri is defined by the tuple (φi , Si ) , where: φi is a semantic concept for the role; Si = {s1 , . . . , sl } is the set of services associated to the role. Each service is defined by the tuple si = (Ii , Oi , Pi , Efi ), where the components are the set of inputs, outputs, preconditions, and effects of the services, respectively. All of them are semantic concepts that can be defined in different ontologies.@mrebollo UPVSelf–Organized Service Management in Heterogeneous and Dynamic MAS
  • 9. Outline System Definition Homophily-based Network Adaption Process Discussion ConclusionsHomophily-based NetworkValue Homophily as Service Similarity Definition (Value Homophily) Hv (Si , Sj ) = α β ∗ WGI + (1 − β)WGO + (1 − α) β ∗ WGP + (1 − β)WGEff = wij ∈EI wij wij ∈EO wij =α β + (1 − β) + max |Ii |, |Ij | max |Oi |, |Oj | wij ∈EP wij wij ∈EEf wij +(1 − α) β + (1 − β) max |Pi |, |Pj | max |Efi |, |Efj |@mrebollo UPVSelf–Organized Service Management in Heterogeneous and Dynamic MAS
  • 10. Outline System Definition Homophily-based Network Adaption Process Discussion Conclusions Homophily-based Network Value Homophily as Service Similarity !"## !"# !"## !"# C1 C1 C4 C1 ω15 = 0.5 C4 C4 C1 0.5 C4 The value homophily function Hv (Si , Sj ) calculates the ω25 = 0.75 C2 degree of matching betweenC5 C2 C2 C5 two set of services, where S C2 0.75 i C5 C5 and Sj are the sets of services provided by the agents0.75 and ω = ai C3C3 aj , respectively. In general, the C6 level of matching 36 0.75 C6 C3 C3 between to C6 C6 sets of semantic concepts Ci and Cj is calculated through a G G bipartite matching!graph. Let G = (Ci , Cj , E)G = a( !"#,#!"# , E) G = ( "## !",# E) , be complete, weighted, bipartite graph that links each concept ci ∈ Ci to each concept cj with Cj . ωij values Table ∈ the represents the weight associated to the arc ei = "#! i , cj ) ∈ E between !i"#$%$&()*(+)*(+),-.$%$(/+$ ! (c "$! "%! c and cj as the semantic similarity between ()$! concepts. Four degrees of "&! ()$! ($! thoseExpRandom ")! be! identified: exact, subsumes, plug-in, and matching can Join( (*$! ! fail [18]. The "+! match is considered as exact, if c1 ∈ Ci is ($! ()$! (*$! ! equivalent to c2 ∈ Cj (c1 ≡ c2 ); subsumes, if c1 subsumes @mrebollo UPV c (c ❂ Service Management in Heterogeneous subsumed by c (c ❁ c ); Self–Organized c ); plug-in, if c is and Dynamic MAS
  • 11. Outline System Definition Homophily-based Network Adaption Process Discussion ConclusionsHomophily-based NetworkStatus Homophily as Role Similarity Definition (Status Homophily) Hs (Ri , Rj ) = max (rmatch(φi , φj )) ri ∈Ri ,rj ∈Rj where (Fu et al. 2009)   1  if path length = 0 rmatch(φi , φj ) = e (−λ(pl+pc)) ∗ δ if roles no siblings  (−λ(pl−d))  e ∗δ if roles siblings and e γdp − e −γdp δ= e γdp + e −γdp@mrebollo UPVSelf–Organized Service Management in Heterogeneous and Dynamic MAS
  • 12. Outline System Definition Homophily-based Network Adaption Process Discussion ConclusionsHomophily-based NetworkStatus Homophily as Role Similarity FilmRecommender pl = 7 BookRecommender cp = 3 Recommender d=2 Leisure MusicRecommender superclasses = 3 superclasses = 4 LeisureOrganizer max depth = 6 TravelAgency Informative HotelsManager TouristInformation GeoInfo Location PreparedFoodProvider WeatherMan Food Thing Supplier FoodProvider FreshFoodProvider Drink Supplier Supplier CarSeller VehicleSeller CycleSeller Seller CameraSeller BookSeller UniversityStaff Occupational Work Occupation SciencePublisher Information Publication NovelPublisher@mrebollo UPVSelf–Organized Service Management in Heterogeneous and Dynamic MAS
  • 13. Outline System Definition Homophily-based Network Adaption Process Discussion ConclusionsHomophily-based NetworkCommunity Creation Definition (Choice Homophily) CH(ai , aj ) = ϕ ∗ Hs (Ri , Rj ) + (1 − ϕ) ∗ Hv (Si , Sj ) The ϕ parameter regulates the importance of the influence of roles (status homophily) or services (value homophily) in the total homophily of the agent with its neighbors.@mrebollo UPVSelf–Organized Service Management in Heterogeneous and Dynamic MAS
  • 14. Outline System Definition Homophily-based Network Adaption Process Discussion ConclusionsHomophily-based NetworkSample of Homophily-based Network Structure@mrebollo UPVSelf–Organized Service Management in Heterogeneous and Dynamic MAS
  • 15. Outline System Definition Homophily-based Network Adaption Process Discussion ConclusionsHomophily-based NetworkDecentralized Service Search Algorithm Neighbor selection function πi (at ) = argmax Ps (aj , at ) aj ∈Ni Where the probability for a neighbor to be chosen depends on its similarity with the desired service (choice homophily) and its degree |Nj | CH(aj , at ) Ps (aj , at ) = 1 − 1 − aj ∈Ni CH(aj , at )@mrebollo UPVSelf–Organized Service Management in Heterogeneous and Dynamic MAS
  • 16. Outline System Definition Homophily-based Network Adaption Process Discussion ConclusionsStructural Homophily as Local Self-Adaptive MethodStructural Homophily Relative importance of an agent based on the services it has served and the queries it has redirected as the value 1 0.9 agent traffic fitted power-law function a*x^b associated to the category ci 0.8 Number of received queries of the most demanded service 0.7 0.6 si ∈ Si : 0.5 0.4 cib 0.3 SH(ai ) = a · 0.2 0.1 0 2 4 6 8 10 12 14 16 Category of the received queries where ci = argmax a · x b x@mrebollo UPVSelf–Organized Service Management in Heterogeneous and Dynamic MAS
  • 17. Outline System Definition Homophily-based Network Adaption Process Discussion ConclusionsStructural Homophily as Local Self-Adaptive MethodAgent Self-Disconnection Each agent decides to leave the network if it is not important for the system to replicate itself if it considers that it is relevant for the network and it has received a significant increment in the number of queries that it receives; or to continue otherwise. Probabilities for adaption function ρi Pψ (leave) = 1 − SH(ai ) Pψ (continue) = Pψ (stay ∩ clone) = SH(ai )f (x ) Pψ (replicate) = Pψ (stay ∩ clone) = SH(ai )(1−f (x ))@mrebollo UPVSelf–Organized Service Management in Heterogeneous and Dynamic MAS
  • 18. Outline System Definition Homophily-based Network Adaption Process Discussion ConclusionsStructural Homophily as Local Self-Adaptive MethodLink Decay 1 n=2 n=4 The utility of the links decay 0.9 0.8 n=6 with time if they are not used 0.7 Probability to maintain the link 0.6 following a sigmoid function 0.5 0.4 1 0.3 dai (qi ) = 1 − −(qi −m) 0.2 0.1 1+l ·e n 0 0 10 20 30 40 50 60 Number of queries that were forwarded to other links@mrebollo UPVSelf–Organized Service Management in Heterogeneous and Dynamic MAS
  • 19. Outline System Definition Homophily-based Network Adaption Process Discussion ConclusionsDiscussionSearch Performance 300 450 role-based EVN role-based EVN EVN EVN Random Random Degree 400 Degree 250 Similarity Similarity 350 200 300 Number of paths Number of paths 250 150 200 100 150 100 50 50 0 0 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 Path length Path length Search performance without role information (left) and combining service and role information in the homophily calculation with ϕ = 0.5 (right)@mrebollo UPVSelf–Organized Service Management in Heterogeneous and Dynamic MAS
  • 20. Outline System Definition Homophily-based Network Adaption Process Discussion ConclusionsDiscussionAgent Self-Disconnection 2500 Original network self-adapted network 1 initial agents distribution agents distribution 0.9 queries distribution 2000 0.8 0.7 Number of paths 1500 0.6 Agents 0.5 1000 0.4 0.3 500 0.2 0.1 0 0 0 10 20 30 40 50 60 70 80 90 100 0 2 4 6 8 10 12 14 16 18 Path length Category With agents deciding to stay, leave or clone, the network adapts to the demand (left) and the average path length is reduced (right)@mrebollo UPVSelf–Organized Service Management in Heterogeneous and Dynamic MAS
  • 21. Outline System Definition Homophily-based Network Adaption Process Discussion ConclusionsDiscussionLink Decay 1 1600 initial agents distribution Original network agents distribution self-adapted and rewired network 0.9 queries distribution 1400 0.8 1200 0.7 1000 Number of paths 0.6 800 Agents 0.5 600 0.4 400 0.3 200 0.2 0.1 0 0 -200 0 2 4 6 8 10 12 14 16 18 0 10 20 30 40 50 60 70 80 90 100 Category Path length Including link decay, the network adapts to the demand (left) but without significant changes in the path length (right).@mrebollo UPVSelf–Organized Service Management in Heterogeneous and Dynamic MAS
  • 22. Outline System Definition Homophily-based Network Adaption Process Discussion ConclusionsConclusionsConclusions What we have done network structure based on homophily as similarity criteria greedy search algorithm with local information adaption of the network without external coordination agents decides to stay or to leave the system link decay Ongoing work: Non-cooperative agents To include agents with different cooperation degree. agents decide to remove links from non-cooperative agents RF strategies to change the behavior to cooperate@mrebollo UPVSelf–Organized Service Management in Heterogeneous and Dynamic MAS