A Framework to Engineer Communities of Web Services Jamal Bentahar Concordia University (Montreal, Canada) Royal Holloway, University of London July 09,

A Framework to Engineer A Framework to Engineer Communities of Web ServicesCommunities of Web Services

Jamal BentaharConcordia University (Montreal, Canada)

Royal Holloway, University of London Royal Holloway, University of London

July 09, 2007July 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

Service Provider

Service RequestorService Broker

Bind(SOAP)

Publish(WSDL) Find

(UDDI)

ServerServer

ClientClientNaming ServiceNaming 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?

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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

• 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

Communities of WSs

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Architecture of WSs Communities

12

Operations for Community Management

LeavingLeaving

WS1WS1

Community of Web Services

JoiningJoining

WS3WS3 WS8WS8

WS6WS6

WS2WS2 WS7WS7

WS4WS4

WS5WS5

• A community of Web services is dynamic by nature:

Temporarily UnavailableTemporarily Unavailable

Resuming operation after

suspension

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

• Community management:1. 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

2. Dismantlement • Number of active WSs

Operations for Community Management

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• Web services:

3. Attraction

• UDDI consultation

• Joining persuasion

4. Retention

• Active behavior

• Collaborative environment

Operations for Community Management

16

Community Management

17

• 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

Development

18

• 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

Attraction and Retention

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• 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

Retention

20

WSCD Protocol

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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

Agent 1Agent 1 Agent 2Agent 2

Negotiation

Persuasion

Cooperation

Conflict solving

…

Negotiation

Persuasion

Cooperation

Conflict solving

…

Conversations: Coherent sequences of utterancesConversations: Coherent sequences of utterances

Reasoning

Capabilities

Reasoning

Capabilities

Reasoning

Capabilities

Reasoning

Capabilities

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• The notion of argument:

a pair <Premises, Conclusion>

• 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

Argumentation

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• Argumentation is a dialectical process

• Attack relation: binary relation between

arguments

Argumentation Dynamics

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Community Management Operations

Argumentative Agent Framework

Dialogue game protocols: specification, implementation, and verification

Global View

Argumentation-based Framework for Communities of WSs

Argumentation-based Framework for Communities of WSs

Communication, Negotiation and Persuasion between WSs

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New Architecture of WSs Communities

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Dialogue Games

• Abstract structures that can be composed:• Sequencing:

• Embedding:

• Parallelization:

• Decision making process

• Computational analysis

Game 1 Game 2,

Game1

Game 2… …

Game 1 Game 2//

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Specification of Dialogue Games

• A persuasion/negotiation protocol

• Specification language

Entry gameExit conditions (Termination)

Chaining gamesChaining games

Action_Ag1 Action_Ag2Cond

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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

Defense game

Attack game

Justification game

t1 t2 t3 t4

Acceptance

Challenge gameAcceptanceChallenge game Attack game

Refusal Termination

Entry game

t0

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• 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 WS’s knowledge bases is finite

Termination Proof

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• Effect of using argumentative agents on

QoS

• Reasoning about small knowledge base is

efficient

• Polynomial time algorithms when using

Horn clauses

Complexity

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• (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

Implementation

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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 Brookes University, Oxford, UKOxford, UK

A Framework to Engineer A Framework to Engineer Communities of Web ServicesCommunities of Web Services

Jamal BentaharConcordia University (Montreal, Canada)

Royal Holloway, University of London Royal Holloway, University of London

July 09, 2007July 09, 2007