1 / 36

Managing Metadata in Service Architectures

Managing Metadata in Service Architectures. Mehmet S. Aktas Advisor: Prof. Geoffrey C. Fox. Outline. Introduction Motivation Requirements Research Issues Architecture Performance Evaluation Conclusions Contribution. Context as Service Metadata. Context interaction-independent

jin
Download Presentation

Managing Metadata in Service Architectures

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Managing Metadata in Service Architectures Mehmet S. Aktas Advisor: Prof. Geoffrey C. Fox

  2. Outline • Introduction • Motivation • Requirements • Research Issues • Architecture • Performance Evaluation • Conclusions • Contribution

  3. Context as Service Metadata • Context • interaction-independent • slowly varying, quasi-static service metadata • interaction-dependent • dynamically generated metadata as result of interaction of services • information associated to a single service, or a session (service activity) or both • Dynamic Grid/Web Service Collections • loosely assembled collections of services • assembled to support a specific task • generate metadata and have limited life-time

  4. Motivating Cases • Multimedia Collaboration Grids • Global Multimedia Collaboration System- Global MMCS • widely distributed services, • session service metadata, session metadata, stream-specific metadata • mostly read-only • Workflow-style applications in Geographical Information System/Sensor Grids • Pattern Informatics (PI) – UC Davis, Interdependent Energy Infrastructure Simulation System (IEISS) – LANL • widely distributed services • conversationmetadata, transient • multiple writers

  5. Problems with Grid Information Services • Standardization and Unification Issues • Customized Grid Information Services • Differences in application requirements • Thick clients • Performance and Centralization Issues • Low performance • Low fault tolerance • Dynamic Metadata Management Issues • Point-to-point service communication approaches

  6. Requirements for Grid Information Services • Greater Interoperability • Unified platform for communication • Shared communication protocol • Thin clients • Greater Capabilities • High Performance • Fault-tolerant • Dynamic Grid/Web Service Collections • Distributed state management • Collaboration session management

  7. Research Issues I • Unification of Grid Information Services • How to combine different information services? • Federation of Grid Information Services • What is a common data model and communication protocol? • Flexibility and extensibility • Accommodating broad range of application domains • read-dominated, read/write dominated • Ability to add/support more information services • Interoperability • Being compatible with wide range of applications

  8. Research Issues II • Performance • Efficient centralized metadata management strategies • high performance and persistency • Efficient decentralized metadata management strategies • Efficient request distribution strategies • Adaptation to instantaneous client-demand changes • Fault-tolerance • Efficient replica-content creation strategies • Consistency • How to provide consistency across the copies of the same data?

  9. Hybrid Grid Information Service • Unification • Uniform Access • Extensibility • Interoperability • Extended UDDI • WS-Context • Federation • Unified Schema • Query/Publish XML API

  10. UDDI instance WS-Context instance Unified schema instance 10 of 34

  11. Decentralized • Fault-tolerant • Efficient distribution • Look-ahead caching • Consistency enforced 11 of 34

  12. Support for interaction-independent metadata: Extended UDDI Service • It supports different types of metadata • Geographical Information System Metadata Catalog (functional metadata) • User-defined metadata ((name, value) pairs) • It enables advanced query capabilities • Geo-spatial queries • Metadata oriented queries • Domain independent queries • It provides additional capabilities • Up-to-date service registry information (leasing) • Dynamic aggregation of capabilities of services • Ex: geospatial capabilities

  13. Support for interaction-dependent metadata: WS-Context Service • Context Manager Service • Data model and communication protocol • Session-related metadata • It supports Dynamic Web Service Collections • Support for distributed state based systems • collaboration grids • workflow-style grids • It provides various capabilities • Asynchronous communication capability • Up-to-date service registry information (leasing)

  14. Support for federated service metadata: Unified Information Service • Federating Grid Information Services • Unified data model and communication protocol • Extended UDDI, WS-Context and Glue Schemas • Approach taken • Union of schemas vs. separate schemas • Reuse common concepts • Ex1: business, session, site => category • Combine disjoined concepts • Ex1: UDDI’s tModel • It enables hybrid query capabilities • “Give me list of services satisfying C:{a,b,c..} QoS requirements and participating S:{x,y,z..} sessions”

  15. Federating Grid Information Services Subscriber Publisher Collaboration Grid Sensor Grid WSDL WSDL HYBRID Service HYBRID Service WS-Context Ext-UDDI Database Database Topic Based Publish-Subscribe Messaging System

  16. Features of the Distributed System • Cache Strategy • Memory-in storage • Access Distribution • Redirecting client request to an appropriate replica server • Look-ahead caching • Moving/replicating metadata to where they wanted • Replica Content Placement • Replicating data on an appropriate replica server • Consistency enforcement • Ensuring all replicas of a data to be the same 16 of 34

  17. Tuple Spaces & Publish-Subscribe Paradigms • Publish-Subscribe paradigm • Message based asynchronous communication • Participants are decoupled both in space and in time • Open source NaradaBrokering software • topic based publish/subscribe messaging system • Tuple Spaces paradigm [Gelernter-99] • a data-centric asynchronous communication paradigm • communication units are tuples (data structure) • JavaSpaces [Sun Microsystems]- object oriented implementation specification

  18. Caching Strategy • Light-weight implementation of JavaSpaces • Data sharing, associative lookup, and persistency • Integrated caching capability for all types of service metadata • Ex: UDDI-type, WS-Context-type, Unified Schema-type metadata • We assume that today’s servers are capable of holding such small size metadata in cache. • All metadata accesses happen in memory • Persistency • All metadata is backed-up into appropriate Information Service back-end every so often for persistency

  19. Persistency investigation 19 of 34

  20. Performance investigation

  21. Message rate scalability investigation

  22. Message size scalability investigation

  23. AccessDistributionLook-ahead Caching • Broadcast-based request dissemination • Pub-sub system for message broadcast • Broadcast requests only to those servers that can answer • No need to keep track of metadata locations • Dynamic migration/replication • [Rabinovich et al, 1999] • Popular copies are moved/replicated where they wanted • Autonomous decisions, self-awareness

  24. Access Distribution ExperimentTest Methodology Time = T1 + T2 + T3 T1 T2 T3

  25. Distribution experiment result • Overhead of access distribution is only few milliseconds. • Continuous access distribution operation does not degrade the performance. • The overhead of distribution remains the same regardless of the network distances between nodes.

  26. Dynamic Replication PerformanceTest Methodology Time = T1 + T2 + T3 T1 T2 T3

  27. The decrease in average latency shows that the algorithm manages to move replica copies to where they wanted.

  28. Replica content placementConsistency enforcement • Replica-content placement • Each node keeps information about other servers • Selection of Replica Server(s) • Selection policy based on a) geographical (proximity) and b) topical (number of topics) information • Consistency Enforcement - Primary-copy approach • Update distribution: updates labeled with synchronized timestamps reflected (unicast) to primary-copy • Update propagation: primary-copy pushes (broadcast) updates only to those replica servers holding the context Hybrid Service 1 Hybrid Service 1 Hybrid Service 2 Hybrid Service 3 Hybrid Service 4

  29. Fault-tolerance experiment Testing Setup Time = T1 + T2 + T3 T1 T2 T3

  30. Fault-tolerance experiment result • Overhead of replica creation is only few milliseconds. • Continuous replica creation operation does not degrade the performance. • Overhead of replica creation increases in the order of milliseconds as the fault-tolerance level increase.

  31. Consistency Enforcement ExperimentTest Methodology Time = T1 + T2 + T3 T1 T2 T3

  32. Consistency Enforcement Test Result • Overhead of consistency enforcement is few milliseconds. • Continuous operation does not degrade the performance. • The cost of consistency enforcement remains the same regardless of distribution of the network nodes.

  33. Conclusions • Efficient centralized metadata management strategies • TupleSpaces Paradigm based memory-in storage • Efficient decentralized metadata strategies • TupleSpaces & Pub-Sub communication paradigms • Distribution • Replication for fault-tolerance • Replication for performance • Consistency Enforcement

  34. Contributions • Unified Grid Information Service Architecture • Flexible and extendable architecture • Support for High Performance and Fault-tolerance • Uniform access to all kinds of service metadata • Federated Grid Information Service Architecture • Unified data model and communication protocol • Support for both interaction independent and conversation-based service metadata • Support for greater interoperability • Efficient decentralized metadata systems can be built by integrating TupleSpaces and Publish-Subscribe paradigms • Fault-tolerance, distribution and consistency can be succeeded with few milliseconds system processing overhead. • Self-awareness can be achieved in decentralized metadata management. • Communication among services can be achieved with efficient mediator metadata strategies • A metadata management approach for Dynamic Web/Grid Service Collections • Collective operations such as queries on subsets of all available metadata in service conversation.

  35. Selected Publication List focusing on a) Metadata, b) Information Services, and c) Metadata Discovery • Mehmet S. Aktas, Geoffrey Fox, Marlon Pierce, Information Services for Dynamically Assembled Semantic Grids [SKG-05, 2005] • Mehmet S. Aktas, Geoffrey Fox, Marlon Pierce, Managing Dynamic Metadata as Context [ICCSE, 2005] • Mehmet S. Aktas et al., Web Service Information Systems and Applications [GGF-16, 2006] • Mehmet S. Aktas, Geoffrey C. Fox, Marlon Pierce, Fault Tolerant High Performance Information Services for Dynamic Collections of Grid and Web Services [FGCS Journal, 2006] • Mehmet S. Aktas, Sangyoon Oh, Geoffrey C. Fox, Marlon Pierce, XML Metadata Services [SKG-2006, Concurrency and Computation: Practice and Experience Journal-2007] • Mehmet S. Aktas, Marlon Pierce, and Geoffrey C.Fox, Designing Ontologies and Distributed Resource Discovery Services for an Earthquake Simulation Grid [ GGF11, 2004] • Mehmet S. Aktas, M. Pierce, G. Fox, and D. Leake , A Web based Conversational Case-Based Recommender System for Ontology aided Metadata Discovery [GRID Workshop -2004] • Sangyoon Oh, Mehmet S. Aktas, Geoffrey C. Fox, Marlon Pierce, Architecture for High-Performance Web Service Communications Using an Information Service [WSEAS Journal -2006]

More Related