A Semantic Web Services Architecture

1
A Semantic Web Services Architecture

• Bayram Kurumahmut
• Ataç Deniz Oral
• Fatih Gön
• 28.12.2005

2
Outline

• About SWSA and their Use Cases
• Introduction
• Service Oriented Computing Components
• Semantic Web Requirements
• Things Architecture Requires
• Phases of Semantic Web Service Interaction
• Service Discovery
• Service Engagement
• Service Enactment
• Community Support Services and Quality of Service
• Conclusion

3
Semantic Web Services Initiative Architecture
Committee (SWSA)

• Objectives
• To identify, through use case analysis, a set of
  key functional elements needed to enable semantic
  web service capabilities.
• To develop abstract protocols.

4
Semantic Web Services Initiative Architecture
Committee (SWSA)

• Milestones
• Working draft of document covering requirements
  and 4 key Use Cases by November 2003.
• Development of a coordinated SWSI submission to
  W3C by January, 2005.

5
SWSA Use Cases

• B2B - Business to Business and in particular
  Enterprise Integration Systems
• Grid - Scientific Grid Computing
• Ubiquitous - Ubiquitous Computing efforts
• Web -Commercial and Informational Web Services
• Agent - Semantic Agent-oriented organizational
  computing

6
Introduction

• Semantic Web Services Architecture
• Semantic WEB
• Web understandable and thus processable by
  machines
• Shared Ontology for eliminating ambiguity
• Ontology Knowledge Representation
• Web Service Architecture based on XML
• Service Description WSDL
• Service Discovery UDDI
• Service Access SOAP

7
Service Oriented Computing Components

• Service Producer
• Advertise the service
• Provide the service
• Service Registry
• Register the service description
• Look up for the service match with the request
• Service Consumer
• Request for a service

8
Semantic Web Agent Requirements

• Dynamic Service Recovery
• Service Engagement
• Service Process Enactment and Management
• Community Support Services
• Quality of Service (QoS)

9
Architectural Requirement Specifications

• Discover services dynamically
• Prepare available service provider list before
  client requests
• Enable service providers update their interfaces
  while client is using same software
  uninterruptedly

10
General Capabilities of Agents

• Accessing and interpreting Web-published
  ontologies
• Semantic Descriptions published by Service
  Providers
• Semantically described service interfaces as
  guides

11
Expected Client Functionalities

• Ability to interpret published semantic
  descriptions.
• Decision making of service usage and
  discovery/substition of new services.

12
Phases of Semantic Web Service Interaction

• Candidate Service Discovery
• Service Engagement
• Service Enactment

13
Service Discovery

• Scan services and list the ones available
• Possible components that achieve this
• Semantic matchmaker
• A registry agent
• A peer agent serving either function

14
Service Engagement

• Evaluate suitable services with their constraints
  until reaching an agreement
• Negotiation components
• Service price
• Product attributes
• Quality and timeliness of service
• Security and privacy

15
Service Enactment

• Monitoring and execution of service
• Address compensation issues in case of abnormal
  termination

16
Client Query

• Manually done by developers
• Effective matching
• More abstract than goal
• Avoid receiving too many candidates
• Includes information
• About how goal should be achieved
• Under which constraints

17
Service Discovery Requirements

• Language
• Help express capabilities and goals
• Service characteristics and constraints
• Preconditions and fulfillment limitations
• Interaction protocols
• Message semantics
• Client requirements
• Goal, quality, security and privacy

18
Service Discovery Requirements (Contd)

• Functional
• Describe capabilities and constraints (provider)
• Abstract service characteristics (client)
• Communicate with matchmaker (client)
• Compare queries with capabilities (matchmaker)
• Select services from candidate services (client)
• Architectural
• Advertising protocols (provider)
• Service selection protocols (client)

19
Service Engagement Requirements

• Functional Requirements
• Service request reformulation (client)
• Exchange goals, capabilities and constraints
• Use aggrement method
• Identify aggrement

20
Service Engagement Requirements (Contd)

• Architectural
• Negotiation protocol
• Negotiation services
• Authentication
• Auditing Services
• Tracking commitments
• Auditing enactment activities

21
Service Engagement Abstract Protocols

• First
• No negotiation
• No formal contract
• Please provide your service for me
• No wait for acknowledgement
• Go to enact step directly
• Second
• Explicit commitment
• Wait for provider response (ack or reject)
• No negotiation

22
Service Engagement Abstract Protocols (Contd)

• Third
• Negotiate on contract
• Wait for commitment
• Explicit shared acknowledgement of contract

Client Will you provide your service for three
dollars? Provider Only if you pay ten
dollars. Client I will pay ten dollars if you
provide your service by 500 pm Provider OK
No
23
Service Enactment

• Completion of the objectives in the contract (the
  outcome of the engagement phase)
• Stakeholders ? Client
• ? Service

24
Service Enactment PhaseRequirements
2 2 4
CLIENT
ß? ? bD
Composition
bD
ß?
SERVICE
Failure Modes
Mediation Service
25
Community Services

• Communally maintained web services
• Information and access security
• Group membership
• Lifecycle management

26
Quality of Service (QoS)

• QoS level agreements must be specified ? deadline
• ? accuracy
• ? cost
• Monitoring of QoS measures

27
Conclusion

• What is proposed?
• SWSA
• What is the objective?
• Interoperability
• What do they claim?
• Compliance with SWSA ? efficient clients
• What is the advantage?
• Maximal freedom

28
The End

• Any questions?