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A model-based validation framework for web services

V. Pretre, F. Bouquet, C. Lang

Laboratoire d’informatique de l’université de Franche-Comté

Besançon, France

STV’07 - Paris, december 5, 2007STV’07 - Paris, december 5, 2007

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Table of contents

Web services qualityWS overview / Relations between WS / Quality of WS

A theoritical solutionModeling / Testing / Certifying quality

The validation frameworkRelations discovery / Pool generation / Tests execution …

Conclusion & future work

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Table of contents

Web services qualityA web services overview

Relations between web services

Quality of web services

A theoritical solution

The validation framework

Conclusion & future work

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Web services qualityAn overview of web services

Principles:client-server application

XML messages

In practice:SOAP encapsulation

http[s]

Linked technologies:WSDL

UDDI

…customer

UDDI

declaration

searchXML messages

Internet

Web service

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Web services qualityRelations between operations

Compositions

A web service operation acts as a client of another one

Several kind of compositions:local/distributed

synchronous/asynchronous

static/dynamic

travel agency

customer

bank hotelairline company

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Web services qualityRelations between operations

Temporal dependencies

An operation can be called only if another one has been called previously

Due to shared datas:server side (database …)

client side

Two types:each time

at least once

database

insertion reading

Customer

results reuse

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Web services qualityQuality of web services

Many definitions:quality of service (accessibility, response time …)

confidentiality of datas

quality of results

Sources of the problem:quality of development

hosting

network

relations between operations

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Table of contents

Web services quality

A theoritical solutionModeling web services behaviour

Test generation and execution

Certification of quality

The validation framework

Conclusion & future work

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A theoritical solutionModeling WS - data used & interface

Done in the class diagram

Two types of classes:datas used by web services

web services interface

Methods used in tests have to be accessible for tester

operations

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A theoritical solutionModeling WS - behaviour of operations

Written in OCL

Defensive modeling:no pre-conditions

errors raised in post-conditions

allows security testing

All behaviours must be modeled

Pre-condition:

self.mission.status = waitingValidationand

self.mission.employee != self.user

Post-condition:

if answer then self.mission.status = validatedelse self.mission.status = refusedendif

if thenif then

result = ok else result = autoValidation endif else result = unvalidableMissionendif

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A theoritical solutionModeling WS - temporal evolution

State-chart diagram

Visual representation of temporal evolution

Complets OCL

userLoggedIn

wsDeployed

validateOk

errorType1 errorType6

errorType2 errorType5

errorType3 errorType4

errorType7

granted

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A theoritical solutionModeling WS - initial state

Instance diagram

At least one instance for each class

Data chosen to:help test generation

cover all possible cases

be representative

Real data needed

Mission::mission1status = waitingValidation

Mission::mission2status = empty

Mission::mission3status = emptyEmployee::fakeEmployee

level=0

Employee::blueLeaderlevel=3

Group::blue

Employee::blueMember1level=4

ValidationRight::blue

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A theoritical solutionTest generation and execution

Tests generated from the model

Tests executed in normal conditions of use

Who executes tests ?customers: many test execution, quality ensured

vendor: only one test execution, customers may not trust in test results

third party: tests results easily shared with customers, but their trust must be obtained

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A theoritical solutionCertification of quality

Two solutions known:only web services that have passed tests are published

The audition framework for testing web services interoperability (Bertolino, Polini )

a mark is given according to tests results Quality attribute for a component quality model (Alvaro, Santana de Almeida,

Romero)

We chose the second solution:one mark by operation

represents the percentage of passed tests

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Table of contents

Web services quality

A theoritical solution

The validation frameworkOverview

Discovering dependencies from model

Computing pools of dependencies

Tests execution

Certification to customers

Conclusion & future work

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The validation frameworkOverview

2 - declaration

3 - treatments of model

4 - test generation5 - creation of test agents

6 - execution

7 - mark computation

8 - WS search

1 - modeling9 - results & marks

Agentcreator

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The validation frameworkDiscovering dependencies

Needed for pools computing

Composition:found in OCL codeonly synchronous

Temporal dependencies:can not be automatically discoveredno common patterns in the state-chartcreation of sequence diagram to describe them

serviceStarted

userLoggedIn

userRegisteredregister()

login() login()

opened

open()save() create()

Client Self

1: register

2: login

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The validation frameworkPools of dependencies

One pool by operationall operations on which it depends

Used to:compute marksplanify test execution

Produced in three stepscreation of the dependency graphcomputation of transitive enclosureeach neighbour of an operation belongs to its pool

open tag categorize publish

save prePublish

create

login

register ping

open tag categorize publish

save prePublish

create

login

register ping

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The validation frameworkTests execution

Tests splitted into waves:operations without dependencies

operations depending on previously tested operations

….

Possible because dependency graph is a DAG

Executed by agents dispatched on the Internet

open tag categorize publish

save prePublish

create

login

register ping

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1

2

3

4

open tag categorize publish

save prePublish

create

login

register ping

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The validation frameworkMark computing

A temporary mark obtained from tests

Final mark based on pools of dependencies (lowest mark of the pool)

shows problems not raised by tests

quick update of mark with new versions

open tag categorize publish

save prePublish

create

login

register ping95

100

100

50

90 90 95 100

80

100

95

95

95

50

50 80 80 80

80

100

open tag categorize publish

save prePublish

create

login

register ping

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Table of contents

Web services quality

A theoritical solution

The validation framework

Conclusion & future workConclusion

Known issues

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Conclusion

The theoritical approach:based on an UML modeling solution (wide spread language)

unique model for behaviour, compositions & temporal dependencies

The framework :Concrete application of the theoritical approach

easy to use for vendors and customers:• based on a norm (UDDI)• marks easy to understand• no modification for the web services or deploiment framework

any kind of web service can be found on the UDDI server

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Known issues & future work

The framework is not completly implemented:missing links between UDDI server and test generator

tool for model merging in case of distributed composition

The mark may not be fully representative3 tests and one fail => 66%

100 tests and 34 fails => 66%

All web services can not be tested and certified