Semantic Web Service Architecture by rogerholland

VIEWS: 0 PAGES: 26

									       Introduction to
    Semantic Web Service
        Architecture
►   The vision of the Semantic Web

►   Ontologies as the basic building block

►   Semantic Web Service Architecture

►   Phases of Semantic Web Services
              The Vision
                            500 million users
                            more than 3 billion pages




Static
         WWW
         URI, HTML, HTTP
              The Vision
                 Serious Problems in
                     ►   information finding,
                     ►   information extracting,
                     ►   information representing,
                     ►   information interpreting and
                     ►   and information
                         maintaining.




Static
         WWW                           Semantic Web
         URI, HTML, HTTP               RDF, RDF(S), OWL
                The Vision


Dynamic    Web Services
           UDDI, WSDL, SOAP   Bringing the computer back
                              as a device for computation




  Static
           WWW                Semantic Web
           URI, HTML, HTTP    RDF, RDF(S), OWL
                   The Vision
           Bringing the web to its full potential



Dynamic    Web Services                      Semantic Web
           UDDI, WSDL, SOAP                  Services




  Static
           WWW                               Semantic Web
           URI, HTML, HTTP                   RDF, RDF(S), OWL
 Deficiencies of WS Technology
► current technologies allow usage of Web Services
► but:
     only syntactical information descriptions
     syntactic support for discovery, composition and execution
    => Web Service usability, usage, and integration needs to
     be inspected manually
     no semantically marked up content / services
     no support for the Semantic Web

=> current Web Service Technology Stack failed to
  realize the promise of Web Services
       Semantic Web Services
            Semantic Web Technology
             • allow machine supported data interpretation
             • ontologies as data model

                             +

             Web Service Technology
            automated discovery, selection, composition,
            and web-based execution of services



=> Semantic Web Services as integrated solution for
  realizing the vision of the next generation of the
  Web
            SWSA: What is it about?
►   SWSA (Semantic Web Services Initiative Architecture) has
    created a set of architectural and protocol abstractions that
    serve as a foundation for Semantic Web service
    technologies.
►   This paper describes the protocols exchanged between the
    interacting entities or agents that interpret and reason with
    semantic descriptions in the deployment of Semantic Web
    services.
              Terminologies Used

►   Web Service - software system designed to support
    interoperable machine-to-machine interaction over a
    network.
►   Semantic Web Service - layer on top of the web service
    infrastructure to supply semantic meaning for web
    services.
►   Agent – software
     SWSA Architectural Framework

►    Addresses five classes of Semantic Web agent
     requirements:
    1. Dynamic Service Discovery
    2. Service Engagement
    3. Service process enactment
    4. Community support services
    5. Quality of service
                     Assumptions
►   Agents can access, interpret and communicate using
    ontologies
►   Service providers publish semantic descriptions of service
    capabilities and interaction protocols..
►   Requesting agents delegate internal objectives as requests
    to service providers.
Phases of Semantic Web Service
          Interaction

► Candidate service discovery
► Service engagement
► Service enactment
Service interaction process.
                   Service Discovery

►   Process of identifying candidate services by clients to achieve their
    objectives.
►   Stakeholders:
          Service providers, use published protocol
          Service requestors, use query protocol
          Matchmakers


►   Service discovery requirements:
          Language requirements
          Functional requirements
          Architectural requirements
              Language requirements

►   For expressing capabilities and goals
      Services’ characteristics and constraints
      Message semantics (protocol during interaction)
      Requester requirements (goal, quality, security and
       privacy)
                 Functional Requirements

►   What are the task for each entity ?
     Providers must describe the capabilities and constraints on offered
      services
     Requestors must create abstract characterizations of required
      services to facilitate matching with published capabilities.
     Requestors must locate and interact with peers or matchmakers
      that can respond to queries for advertised service descriptions.
     Matchmakers must compare descriptions of queries and
      capabilities.
     Requestors must decide if they can satisfy the preconditions
      specified in a prospective service’s self-description in order to use
      it.
             Architectural requirement

 advertising protocols used by service providers
 candidate service-discovery protocols used by
  requestors

Why needed?
 Identify the various classes of agents for final result
               Service Engagement
► Initial phase of interaction between requestor and
  potential provider.
► Results in an agreement.
► Service engagement requirements:
        Functional requirements
          o   Service request Formulation
          o   Contract preliminaries
          o   Contract Negotiation
          o   Agreement
         Architectural requirements
          o Negotiation protocols
          o Negotiation services
          o Auditing services
Engagement message semantics
              Negotiation Protocols
►   FIPA query-reply protocol (equivalent to)
        ► Agreewith no acknowledgement and
        ► No negotiation


►   FIPA request protocol (equivalent to)
        ► Agree or refuse
        ► No negotiation
        ► But commitment to provide a service


►   negotiate-commitment
        ►A  formal negotiations
        ► No party left hanging
        ► Shared acknowledgement of a contract or commitment between them
Negotiate – Commitment Protocol
                     Service Enactment
►   Service is ready to be initiated.
►   Requestor determines the information necessary to request
    performance of service and appropriate reaction to service success
    or failure.
►   Service enactment requirements:
           Functional requirements
              o   Response interpretation
              o   Response translation
              o   Process mediation and delegation
              o   etc
            Architectural requirements
              o   Process mediation services
              o   Process scheduling and composition services
              o   Process execution and status logging services
              o   Policy monitoring services
             Enactment Protocols
►   Three types enactment protocols
      One assume synchronous communication
      Other two assume asynchronous communication
       Community support services

►   Another class of infrastructure services needed to
    support communally maintained semantic web service
    activities. Need Services for
     Authenticated definitions and mappings among concepts
      (ontology) and their derivatives.
     information and access security, privacy, and confidentiality
      management.
     community-based preference and reliability reporting based on
      collected feedback from service clients.
     policy and protocol management as well as validation and
      dispute resolution.
     lifecycle management.
                  Quality of Service

►   Enforcement of QoS metrics
     Can be topic of negotiation processes,
     must be monitored during enactment;
►   Enforcement of QoS-level agreements,
     deadlines, accuracy, and cost.

►   Currently under study
►   Not addressed in detail by SWSA committee.
                         References
►   Mark Burstein, Christoph Bussler, Michal Zaremba, Tim Finin, Michael
    N.Huhns, Massimo Paolucci, Amit P. Sheth, Stuart Williams, “ A
    Semantic Web Services Architecture”, IEEE Internet Computing,
    September-October, 2005

								
To top