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Dynamic Service Composition in Pervasive Computing

Dynamic Service Composition in Pervasive Computing. Swaroop Kalasapur , Member, IEEE, Mohan Kumar, Senior Member, IEEE, and Behrooz A. Shirazi , Member, IEEE IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS, VOL. 18, NO. 7, JULY 2007 報告者 :69721022 陳吉國. Outline. Introduction

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Dynamic Service Composition in Pervasive Computing

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  1. Dynamic Service Compositionin Pervasive Computing SwaroopKalasapur, Member, IEEE, Mohan Kumar, Senior Member, IEEE, andBehrooz A. Shirazi, Member, IEEEIEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS, VOL. 18, NO. 7, JULY 2007 報告者:69721022 陳吉國

  2. Outline Introduction System Architecture Service Model Service Aggregation Hierarchical Service Overlay For Composition Analysis of Dynamic Service Composition Conclusions and Future Work

  3. Introduction Pervasive Computing - 這一概念強調和環境融為一體的計算，而電腦本身則從人們的視線裡消失。在普適計算的模式下，人們能夠在任何時間、任何地點、以任何方式進行信息的獲取與處理，而與一般的行動計算(Mobile computing)不同在於具有情境感知(Context aware)的特性。普及運算技術可以透過感應個人所在的位置、所處的環境資訊、個人的情形及任務，來提供最有效能的使用環境。 因growing applications, pervasive computing 面臨動態的挑戰, 如異質性, 資源限制, mobility, 而Serivce-oriented 環境可保證flexibility和好的資源使用

  4. Introduction Service composition mechanisms - Combine two or more services together to form a complex service, treated as extensions to service discovery technique

  5. System Architecture Centralized directory(Service Location Protocol) Distributed directory(Jini)

  6. Service Model Aim at capturing the feature and useful characteristics of resources in a pervasive environment PCIO(Pervasive Information Communities Organization) middleware - event-oriented - provide a transparent platform for application and service operate on and cooperate with each other

  7. Service Model Device model - capture the characteristics and features of the available hardware resources delegents(intelligent delegates, software entities) - identified features in the device model are provided as services over the network communities - many delegents combine into a cooperative structure

  8. Service Model Service Representation - - : service itself - : input and output for the service - : vertex attribute function, including semantic description of service, location, cost of utilization…… - : edge attribute, including semantic description of parameter, parameter type, data rate, format……

  9. Service Model

  10. Service Model Task Represent - - : service required to accomplish the task - : transition among the service - : vertices attribute, including location, cost, acceptable delay…... - : attribute along he edges, including semantic description of data, data formats, data rates, quality requirements……

  11. Service Model

  12. Service Aggregation All the services present within within a pervasive computing environment are registered with a directory The service graphs(Gs) are parsed for storage into a two-layered aggregation graph Gp - base on the semantic parameters associated with the service - base on the syntactic type of parameters

  13. Service Aggregation

  14. Service Aggregation

  15. Service AggregationTask Resolution (4a)ensure that the output produced by S1 can be consumed by S2 (4b)output attributes of S1 can be completely accepted by S2

  16. Service AggregationTask Resolution

  17. Service AggregationTask Resolution Task Resolution is performed in two steps - one or more possible compositions are derived at the semantic level based on the aggregate graph -If a composition is possible at the semantic level, the underlying services that can take part in the composed result are identified at the second level of aggregation

  18. Service AggregationTask Resolution the semantic mappings of the input semantic parameters to the nodes in the aggregation are identified a corresponding path needs to be identified in , and locating the shortest path from a to b

  19. Service AggregationTask Resolution

  20. Service Aggregation discover + match technique - The user task is represented as a task graph and is sent to the directory for resolution, the services specified within the task graph (denoted by the vertex set Vr) are matched against the services that are registered to identify available matches.

  21. Service Aggregation considered services that perform transformation between two alphabets. A service si is represented as a-> b if si accepts an input of type a and produces an output of type b, so there are 625 unique services

  22. Service Aggregation

  23. Hierarchical Service Overlay For Composition within pervasive computing environments, it is not always possible to assume the support of an infrastructure

  24. Hierarchical Service Overlay For Composition

  25. Hierarchical Service Overlay For Composition Latching - The organization of resources into a service overlay is facilitated by a process - The basic principle of latching is that a device with lower resource availability latches itself to another device with higher resource availability - detailed as a protocol

  26. Hierarchical Service Overlay For Composition

  27. Hierarchical Service Overlay For Composition The resulting hierarchical overlay is maintained with periodic LATCH_HELO messages, along which the current status of the child nodes is relayed to the parent a lower level will rely on their higher level counterparts (parents) for essential operations such as service discovery, composition, proxy operation, and so forth

  28. Hierarchical Service Overlay For CompositionHierarchical Aggregation of Services When a new device A joins the hierarchy, the parent B will collect the graphs for all the services provided by A and updates the local service aggregation LATCH_ADD LATCH_REM

  29. Hierarchical Service Overlay For CompositionHierarchical Aggregation of Services

  30. Hierarchical Service Overlay For CompositionHierarchical Aggregation of Services Service zone - The service zone of a deviceDincludesall the children of D within the hierarchy and itself Search zone - The search zone of a device D is its own service zone if > 1 , If < 1, then the search zone of D is the service zone of parent(D)

  31. Hierarchical Service Overlay For CompositionHierarchical Aggregation of Services

  32. Hierarchical Service Overlay For Composition When a particular task needs to be accomplished, based on the of the device generating the request, the task resolution process begins either at the same device or at its immediate parent

  33. Analysis of Dynamic Service Composition Service-related factor - Locality of Service - Quality-Aware Composition - User and Resource mobility

  34. Analysis of Dynamic Service Composition Locality of Service - all involved services need to as close to each other as possible Quality-Aware Composition - employ a limited version of MCPS by limiting the length of composition

  35. Analysis of Dynamic Service Composition

  36. Analysis of Dynamic Service Composition User and Resource mobility - When the user moves to a new location, the first task is to identify a suitable service that can directly interact with the user - a new composition can be generated to meet the requirements of the affected node in at most two search zone expansions and another lookup on among the level-3 devices

  37. Analysis of Dynamic Service Composition

  38. Conclusions and Future Work performance better than traditional discover + match model that would capture information about the available resources in a dynamic fashion

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