Semantic Web Service Architecture

1
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

2
The Vision

• 500 million users
• more than 3 billion pages

WWW URI, HTML, HTTP
Static
3
The Vision

• Serious Problems in
• information finding,
• information extracting,
• information representing,
• information interpreting and
• and information maintaining.

WWW URI, HTML, HTTP
Semantic Web RDF, RDF(S), OWL
Static
4
The Vision
Web Services UDDI, WSDL, SOAP
Dynamic

• Bringing the computer back as a device for
  computation

WWW URI, HTML, HTTP
Semantic Web RDF, RDF(S), OWL
Static
5
The Vision

• Bringing the web to its full potential

Semantic Web Services
Web Services UDDI, WSDL, SOAP
Dynamic
WWW URI, HTML, HTTP
Semantic Web RDF, RDF(S), OWL
Static
6
Deficiencies of WS Technology

• current technologies allow usage of Web Services
• but
• only syntactical information descriptions
• syntactic support for discovery, composition and
  execution
• gt Web Service usability, usage, and integration
  needs to be inspected manually
• no semantically marked up content / services
• no support for the Semantic Web
• gt current Web Service Technology Stack failed to
  
• realize the promise of Web Services

7
Semantic Web Services

• Semantic Web Technology
• Web Service Technology

• allow machine supported data interpretation
• ontologies as data model

automated discovery, selection, composition, and
web-based execution of services
gt Semantic Web Services as integrated solution
for realizing the vision of the next generation
of the Web
8
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.

9
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

10
SWSA Architectural Framework

• Addresses five classes of Semantic Web agent
  requirements
• Dynamic Service Discovery
• Service Engagement
• Service process enactment
• Community support services
• Quality of service

11
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.

12
Phases of Semantic Web ServiceInteraction

• Candidate service discovery
• Service engagement
• Service enactment

13
Service interaction process.
14
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

15
Language requirements

• For expressing capabilities and goals
• Services characteristics and constraints
• Message semantics (protocol during interaction)
• Requester requirements (goal, quality, security
  and privacy)

16
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
  services self-description in order to use it.

17
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

18
Service Engagement

• Initial phase of interaction between requestor
  and potential provider.
• Results in an agreement.
• Service engagement requirements
• Functional requirements
• Service request Formulation
• Contract preliminaries
• Contract Negotiation
• Agreement
• Architectural requirements
• Negotiation protocols
• Negotiation services
• Auditing services

19
Engagement message semantics
20
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

21
Negotiate Commitment Protocol
22
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
• Response interpretation
• Response translation
• Process mediation and delegation
• etc
• Architectural requirements
• Process mediation services
• Process scheduling and composition services
• Process execution and status logging services
• Policy monitoring services

23

Enactment Protocols

• Three types enactment protocols
• One assume synchronous communication
• Other two assume asynchronous communication

24
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.

25
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.

26
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