A%20Framework%20to%20Engineer%20Communities%20of%20Web%20Services

1
A Framework to Engineer Communities of Web
Services

• Jamal Bentahar
• Concordia University (Montreal, Canada)

Royal Holloway, University of London July 09,
2007
2
Overview

• Context and Motivations
• Communities of Web Services Definitions
• Communities of Web Services Engineering
• Argumentation between Web Services
• Conclusion and Future Work

3
Context

• Web services (WSs) A new breed of Web
  application
• Self-contained
• Self-describing
• Can be published, located, and invoked across the
  Web
• Functions anything from simple requests to
  complicated business processes
• Once a Web service is deployed, other
  applications (and other Web services) can
  discover and invoke the deployed service

4
Technologies

• Web service (WS)
• Software application identified by a URI
• XML artifacts Interface definition and
  discovering
• Web Service Description Language (WSDL)
• Universal Description, Discovery, and Integration
  (UDDI) registry, ebXML
• Simple Object Access Protocol (SOAP)
• SOAP defines a common standard that allows
  different systems to interoperate

5
Standards and Projects

• Standards for Services definition, discovery, and
  security
• Projects for Web services composition,
  personalization, and contextualization
• Composition
• A user's request cannot be satisfied by any
  single, available Web service
• A composite Web service obtained by combining
  available Web services may be used

6
Service-Oriented Architecture
Server
Service Provider
Bind (SOAP)
Publish (WSDL)
Find (UDDI)
Service Requestor
Service Broker
Client
Naming Service
7
Motivations

• Communities of Web services
• Gathering WSs with similar functionalities (e.g.
  FlightBooking)
• How to initiate, set up, and specify a community
  of WSs?
• How to specify and manage the WSs that reside in
  a community?
• How to conciliate conflicts within a community
  and between communities?

8
Motivations

• What can agent technology do for communities of
  WSs?
• The notion of agent software-based computer
  system that enjoys the following properties
• Autonomy
• Reactivity
• Pro-activeness
• Social ability
• Interest of agent reasoning and communication
  capabilities

9
Overview

• ? Context and Motivations
• Communities of Web Services Definitions
• Communities of Web Services Engineering
• Argumentation between Web Services
• Conclusion and Future Work

10
Communities of WSs

• Collection of WSs with a common functionality
• These WSs could have distinct non-functional
  properties
• A means for providing a common description of a
  desired functionality
• Objective To ease and improve the process of Web
  services discovery and composition

11
Architecture of WSs Communities
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Operations for Community Management

• A community of Web services is dynamic by
  nature

Community of Web Services
Temporarily Unavailable

Joining
WS4
WS1
WS6
WS2
WS7
WS5
Leaving
WS3
WS8
Resuming operation after suspension
13
Overview

• ? Context and Motivations
• ? Communities of Web Services Definitions
• Communities of Web Services Engineering
• Argumentation between Web Services
• Conclusion and Future Work

14
Operations for Community Management

• Community management
• Development
• Functionality definition
• Master WS deployment
• A dedicated Web service plays the role of master
  for the time being of a community
• Identifying a Web service from the list of Web
  services populating a community to act as a
  master
• Dismantlement
• Number of active WSs

15
Operations for Community Management

• Web services
• Attraction
• UDDI consultation
• Joining persuasion
• Retention
• Active behavior
• Collaborative environment

16
Community Management
17
Development

• Master WS leads the community
• Inviting and convincing Web services to sign up
  in the community
• Checking the credentials of Web services before
  they get admitted

18
Attraction and Retention

• A master WS responsibility
• Attracting new Web services to and retaining
  existing Web services in a community
• Consulting UDDI and checking the functionality
  description of existing WSs

19
Retention

• Web services in a community should expose a
  cooperative attitude
• Web services should be aware of some peers in the
  community that could replace them in case of
  failure
• Web service should be satisfied with their
  participation rates in composite Web services

20
WSCD Protocol
21
CN Protocol WS Selection
22
Master WS Architecture
23
Slave WS Architecture
24
Protocol Interactions
25
Overview

• ? Context and Motivations
• ? Communities of Web Services Definitions
• ? Web Services Communities Engineering
• Argumentation between Web Services
• Conclusion and Future Work

26
Agents for WSs
Reasoning Capabilities
Reasoning Capabilities
Agent 2
Agent 1
Negotiation Persuasion Cooperation Conflict
solving
27
Argumentation

• The notion of argument
• a pair ltPremises, Conclusiongt
• An argument is a pair (P, c) where P is a set of
  beliefs and c is a formula, such that
• i) P is consistent, ii) P c

28
Argumentation Dynamics

• Argumentation is a dialectical process
• Attack relation binary relation between
  arguments

29
Global View
Argumentation-based Framework for Communities of
WSs
Community Management Operations
Communication, Negotiation and Persuasion between
WSs
Argumentative Agent Framework
Dialogue game protocols specification,
implementation, and verification
30
New Architecture of WSs Communities
31
Dialogue Games

• Abstract structures that can be composed
• Sequencing
• Embedding
• Parallelization
• Decision making process
• Computational analysis

Game 1
Game 2
,
//
Game 1
Game 2
32
Specification of Dialogue Games

• A persuasion/negotiation protocol
• Specification language

33
Entry Game
34
Defense Game
35
Attack Game
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PNAWS Protocol

• PNAWS Persuasion/Negotiation for Agent-based Web
  Services protocol
• BNF grammar

37
Protocol Dynamics

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Termination Proof

• For any dialogue games, the PNAWS protocol always
  terminates
• Recursive definition
• The same move is prohibited
• The content of communicative acts is finite
• Challenge and attack moves are finite
• The agent-based WSs knowledge bases is finite

39
Complexity

• Effect of using argumentative agents on QoS
• Reasoning about small knowledge base is efficient
• Polynomial time algorithms when using Horn
  clauses

40
Implementation

• (1) XML used for request and response
  specification between users and WSs and also
  between master WS and slave WSs
• (2) JDK 1.4 used for operation processing,
• (3) Jack for argumentative agents and dialogue
  games
• (4) Eclipse 3.1 as an integrated development
  environment

41
Implementation System Architecture
42
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Conclusion

• From WSs to Communities of WSs
• Specification and development of an
  argumentation-based framework for communities of
  WSs
• Advantages
• Autonomous and flexible WSs and composite WSs
• Intelligent and dynamic WSs

44
Future Work

• Specifying other protocols using the developed
  framework
• Defining operational and denotational semantics
  for these protocols
• Verifying these protocols by model checking
• Developing security policies for the communities

45
Collaborators

• Zakaria Maamar Zayed University, Dubai, United
  Arab Emirates
• Djamal Benslimane Claude Bernard Lyon 1
  University, Lyon, France
• Philippe Thiran University of Namur, Namur,
  Belgium
• Sattanathan Subramanian University of Namur,
  Namur, Belgium
• Muhammad Younas Oxford Brookes University,
  Oxford, UK

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A Framework to Engineer Communities of Web
Services

• Jamal Bentahar
• Concordia University (Montreal, Canada)

Royal Holloway, University of London July 09,
2007