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

Static  500 million users  more than 3 billion pages WWW URI, HTML, HTTP The Vision

WWW URI, HTML, HTTP Serious Problems in ► information finding, ► information extracting, ► information representing, ► information interpreting and ► and information maintaining. Semantic Web RDF, RDF(S), OWL Static The Vision

WWW URI, HTML, HTTP Bringing the computer back as a device for computation Semantic Web RDF, RDF(S), OWL Dynamic Web Services UDDI, WSDL, SOAP Static The Vision

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

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 realize the promise of Web Services

Semantic Web Technology + Web Service Technology Semantic Web Services => Semantic Web Services as integrated solution for realizing the vision of the next generation of the Web allow machine supported data interpretation ontologies as data model automated discovery, selection, composition, and web-based execution of services

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 oService request Formulation oContract preliminaries oContract Negotiation oAgreement  Architectural requirements o Negotiation protocols o Negotiation services o Auditing services

Engagement message semantics

Negotiation Protocols ► FIPA query-reply protocol (equivalent to) ► Agree with 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 oResponse interpretation oResponse translation oProcess mediation and delegation oetc  Architectural requirements oProcess mediation services oProcess scheduling and composition services oProcess execution and status logging services oPolicy monitoring services

► Three types enactment protocols  One assume synchronous communication  Other two assume asynchronous communication Enactment Protocols

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