1. 1 8 October 2015 Coordination middleware for decentralized applications in dynamic networks Kurt Schelfthout, Tom Holvoet

2. 2 8 October 2015 Elevator Talk Dynamic networks oChanging composition over time Decentralized applications oApplication components spread over the network nodes ono single component has global control Coordination both important and difficult for application developer Coordination support needed oAppropriate abstractions oSupport abstractions through middleware

3. 3 8 October 2015 Overview Case Study oAutomatic Guided Vehicle control Views ogather and maintain context information Roles osetup and maintain a group of components interacting through a protocol

4. 4 8 October 2015 Example Application

5. 5 8 October 2015 Description of purpose Decentralization oCollision avoidance oDeadlock avoidance oJob assignment Dynamic network oMobility of AGVs Coordination oSupport a higher level of abstraction wrt “message sending” oDeal with network dynamics

6. 6 8 October 2015 Goal Statement Develop oAbstractions for the coordination of application components oSupported by middleware Advantages oOffers a suitable architecture to structure application oAllows reuse of common functionality oAccelerates application development

7. 7 8 October 2015 Methodology Case-driven oAnalyse case oPropose abstraction oDevelop middleware oEvaluate in case study Two iterations oViews for information gathering in mobile ad hoc networks oRoles for protocol-based coordination in mobile networks

8. 8 8 October 2015 Views Node

9. 9 8 October 2015 Views Application components use otuplespace for publishing information tuples oView for gathering information tuples Declarative description  Which nodes? Which tuples?  E.g. ‘gather all printers within 30 meters’ Middleware collects the tuples in the view oAs network changes oAs content of tuplespaces changes

10. 10 8 October 2015 Related Work Tuplespaces-based systems oLIME: shared tuplespaces oEgoSpaces: views oTOTA: Distributed tuples Publish/subscribe-based systems oSTEAM : Location-dependent subscriptions oJEDI: moveIn and moveOut operator Related to both oView ~ gathering of tuples from neighboring tuplespaces oView ~ subscription on events on neighboring tuplespaces

11. 11 8 October 2015 Colllision Avoidance in AGV case

12. 12 8 October 2015 Colllision Avoidance in AGV case

13. 13 8 October 2015 Colllision Avoidance in AGV case

14. 14 8 October 2015 Colllision Avoidance in AGV case

15. 15 8 October 2015 Views for collision avoidance? Can be used as “discovery mechanism” oDetect possible overlapping hulls But: complex coordination oInvolving more than information exchange oMutual exclusion protocol needed

16. 16 8 October 2015 Roles Behavior of one partner in an interaction protocol To describe object collaborations in OO oFramework design oOO related languages (EpsilonJ) oRole pattern To describe protocols in multi-agent systems

17. 17 8 October 2015 Roles Node Initiator Node Participant

18. 18 8 October 2015 Roles for protocol-based interaction Group odeclaratively describes with which nodes to execute the protocol oDetermines activation of roles Middleware maintains groups of activated roles oExecuting an interaction session oGroup is updated as network changes

19. 19 8 October 2015 Collision avoidance revisited

20. 20 8 October 2015 Activation of Roles

21. 21 8 October 2015 Colllision Avoidance in AGV case

22. 22 8 October 2015 Colllision Avoidance in AGV case Start Requester Role

23. 23 8 October 2015 Colllision Avoidance in AGV case requester voter

24. 24 8 October 2015 Colllision Avoidance in AGV case requester voter Request(Hull)

25. 25 8 October 2015 Colllision Avoidance in AGV case requester voter Deny

26. 26 8 October 2015 Colllision Avoidance in AGV case Requester (waiting)

27. 27 8 October 2015 Evaluation: Views Developed protocol to support views in a MANET Experiments oAnalytically & in a simple MANET similator  Overhead: <10%  Correctness: best-effort, very dependent on mobility of nodes oIn progress: ns-2 simulations  More realistic  Comparison with related protocols Application oUpdating network stacks in an active network oE.g. dynamically adding compressor/decompressor to improve quality of service

28. 28 8 October 2015 Evaluation: Roles Real world application: Automatic Guided Vehicle control oRole-based middleware used throughout  Collision avoidance, deadlock avoidance, job assignment,… Gain experience Real life testing  2 vehicles in test setup  More vehicles in simulation Not “just” prototype implementation

29. 29 8 October 2015 Thank you! Questions?