Web service architectureWeb services selection

Proposed modelConclusion

Multicriteria Evaluation Based Framework forComposite Web Service Selection

Samir Youcef and Salem Chakhar

Laboratoire d’Analyse et de Modélisationdes Systèmes pour l’Aide à la Décision

Université de Paris-Dauphine21 February 2008

youcef, chakhar@lamsade.dauphine.fr

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Elementary Web Service

Web service definition (W3C)

B Web service is a software system designed to supportinteroperable machine to machine interaction over a network

B Interoperability among services is insured by the openprotocols:

Description: XML (eXtensible Markup language)

Transport: SOAP (Simple Object Access Protocol)

Interface: WSDL (Web Service Description Language)

WSDL is limited to simple operations:

How compose the different operations (Need a standarddescription of the process)

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Composite Web service

Composition languages

WSFL (Web Services Flow Language): IBM

XLANG (XML Business Process Language): Microsoft

PBML (Business Process Modeling Language): BPMI.org

BPEL4WS

BPEL4WS is the merger of WSFL, XLANG et PBML

BPEL4WS constructorsBasic: invoke, receive, reply, wait, assign,...

Structured: sequence, switch, while, flow, pick,...

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Conventional Web service architecture

B A Web service can be discovered in UDDI registry.

SOAP

HTTP,FTP...

Search

UDDI

Publication of the WSDLDecsription

Service customer Service provider

Recuperation of the WSDL description

Bind

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Web services selection

B Composite Web service=A+B+C (What is the best composition?)

Search

UDDI

Publication of the WSDLDecsription

Service customer

Recuperation of the WSDL description

Bind

Service A: provider 1,provider 2.

Service B:

provideer 1,provider 2, provider 3.

Service C: provider 1, provider 2.

Travel site: airline booking, hotel reservation, car reservation

http

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Web services selection

Quality of service (QoS)

QoS is a combinaison of several properties:

Qualitative: security, reputation,...

Quantitative: response time, availability,...

Previous studies

Single evaluation criterion

Successive evaluation ("general level" of differentcomposition)

Local strategy selection

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Web services selection

LimitationsA single criterion does not permit to encompass all thefacets of the problem

Weighted sum-like aggregation rules may lead to thecompensation problem

Several QoS evaluation criteria are naturally qualitative

Proposed solution

Using multicreteria evaluation of the different composition

Extend the conventional Web service architecture, usingQoS

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Extended conventional Web service architecture

Multicriterai Evalutaion?

yesno

infer

evaluate

Multicriteria Evaluation Component (MEC)

W-IRISDecisionDeck

Conventional Evaluation

CustomerProvider

UDDI registry

response responsefind

bind

publish

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Extended conventional Web service architecture

Multicriterai Evalutaion?

yesno

infer

evaluate

Multicriteria Evaluation Component (MEC)

W-IRISDecisionDeck

Conventional Evaluation

CustomerProvider

UDDI registry

response responsefind

bind

publish

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Extended conventional Web service architecture

Multicriterai Evalutaion?

yesno

infer

evaluate

Multicriteria Evaluation Component (MEC)

W-IRISDecisionDeck

Conventional Evaluation

CustomerProvider

UDDI registry

response responsefind

bind

publish

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Extended conventional Web service architecture

Multicriterai Evalutaion?

yesno

infer

evaluate

Multicriteria Evaluation Component (MEC)

W-IRISDecisionDeck

Conventional Evaluation

CustomerProvider

UDDI registry

response responsefind

bind

publish

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Extended conventional Web service architecture

Multicriterai Evalutaion?

yesno

infer

evaluate

Multicriteria Evaluation Component (MEC)

W-IRISDecisionDeck

Conventional Evaluation

CustomerProvider

UDDI registry

response responsefind

bind

publish

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Dynamics of the system

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Definitions

Elementary Web service definition

Web service si , i ∈ 1, .., n is characterized by the tuple:

Fi : description functionality

Qi : specification of its QoS

Ci : cost specification

Pi : set of providers of functionality Fi , i ∈ 1, ..., n

Composite Web service definition

G = (X , V ) composite graphe associated with s1, ..., sn

A composite Web service is an instance s1, ..., sn of G,such: s1 ∈ P1,...,sn ∈ Pn

sji : i th elementary Web service offered by the j th provider

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Potential composite Web services

Algorithm CompositionsConstructionINPUT: G = (X , V ): compositiongraph

P = P1, P2, · · · , Pn: providersOUTPUT: C: potential compositionsT ← Construct −Tree( X , P)t ← 1WHILE t <=

Qni=1 |Pi |

Xt ← ElementaryPath( T )//Xt = s·1, s·2, · · · , s·nFOR each (Sh, Sk ) ∈ V

Vt ← (s·h, s·k )END−FOR

ct ← Gt = (Xt , Vt )C ← C ∪ ctt ← t + 1END−WHILE

r

. . .

. . .

. . .

. . .

s11 s2

1 s31

s41

s12 s2

2 s32

s32s2

2s12

s13 s2

3 s13

s23

s14

s14

s15 s2

5 s35 s4

5 s55

s15 s2

5 s35 s4

5s5

5

s16 s2

6s1

6 s26

. . .

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Potential composite Web services

Algorithm CompositionsConstructionINPUT: G = (X , V ): compositiongraph

P = P1, P2, · · · , Pn: providersOUTPUT: C: potential compositionsT ← Construct −Tree( X , P)t ← 1WHILE t <=

Qni=1 |Pi |

Xt ← ElementaryPath( T )//Xt = s·1, s·2, · · · , s·nFOR each (Sh, Sk ) ∈ V

Vt ← (s·h, s·k )END−FOR

ct ← Gt = (Xt , Vt )C ← C ∪ ctt ← t + 1END−WHILE

r

. . .

. . .

. . .

. . .

s11 s2

1 s31

s41

s12 s2

2 s32

s32s2

2s12

s13 s2

3 s13

s23

s14

s14

s15 s2

5 s35 s4

5 s55

s15 s2

5 s35 s4

5s5

5

s16 s2

6s1

6 s26

. . .

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Potential composite Web services

Algorithm CompositionsConstructionINPUT: G = (X , V ): compositiongraph

P = P1, P2, · · · , Pn: providersOUTPUT: C: potential compositionsT ← Construct −Tree( X , P)t ← 1WHILE t <=

Qni=1 |Pi |

Xt ← ElementaryPath( T )//Xt = s·1, s·2, · · · , s·nFOR each (Sh, Sk ) ∈ V

Vt ← (s·h, s·k )END−FOR

ct ← Gt = (Xt , Vt )C ← C ∪ ctt ← t + 1END−WHILE

r

. . .

. . .

. . .

. . .

s11 s2

1 s31

s41

s12 s2

2 s32

s32s2

2s12

s13 s2

3 s13

s23

s14

s14

s15 s2

5 s35 s4

5 s55

s15 s2

5 s35 s4

5s5

5

s16 s2

6s1

6 s26

. . .

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Potential composite Web services

Algorithm CompositionsConstructionINPUT: G = (X , V ): compositiongraph

P = P1, P2, · · · , Pn: providersOUTPUT: C: potential compositionsT ← Construct −Tree( X , P)t ← 1WHILE t <=

Qni=1 |Pi |

Xt ← ElementaryPath( T )//Xt = s·1, s·2, · · · , s·nFOR each (Sh, Sk ) ∈ V

Vt ← (s·h, s·k )END−FOR

ct ← Gt = (Xt , Vt )C ← C ∪ ctt ← t + 1END−WHILE

r

. . .

. . .

. . .

. . .

s11 s2

1 s31

s41

s12 s2

2 s32

s32s2

2s12

s13 s2

3 s13

s23

s14

s14

s15 s2

5 s35 s4

5 s55

s15 s2

5 s35 s4

5s5

5

s16 s2

6s1

6 s26

. . .

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Potential composite Web services

Algorithm CompositionsConstructionINPUT: G = (X , V ): compositiongraph

P = P1, P2, · · · , Pn: providersOUTPUT: C: potential compositionsT ← Construct −Tree( X , P)t ← 1WHILE t <=

Qni=1 |Pi |

Xt ← ElementaryPath( T )//Xt = s·1, s·2, · · · , s·nFOR each (Sh, Sk ) ∈ V

Vt ← (s·h, s·k )END−FOR

ct ← Gt = (Xt , Vt )C ← C ∪ ctt ← t + 1END−WHILE

r

. . .

. . .

. . .

. . .

s11 s2

1 s31

s41

s12 s2

2 s32

s32s2

2s12

s13 s2

3 s13

s23

s14

s14

s15 s2

5 s35 s4

5 s55

s15 s2

5 s35 s4

5s5

5

s16 s2

6s1

6 s26

. . .

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Potential composite Web services

Algorithm CompositionsConstructionINPUT: G = (X , V ): compositiongraph

P = P1, P2, · · · , Pn: providersOUTPUT: C: potential compositionsT ← Construct −Tree( X , P)t ← 1WHILE t <=

Qni=1 |Pi |

Xt ← ElementaryPath( T )//Xt = s·1, s·2, · · · , s·nFOR each (Sh, Sk ) ∈ V

Vt ← (s·h, s·k )END−FOR

ct ← Gt = (Xt , Vt )C ← C ∪ ctt ← t + 1END−WHILE

r

. . .

. . .

. . .

. . .

s11 s2

1 s31

s41

s12 s2

2 s32

s32s2

2s12

s13 s2

3 s13

s23

s14

s14

s15 s2

5 s35 s4

5 s55

s15 s2

5 s35 s4

5s5

5

s16 s2

6s1

6 s26

. . .

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Potential composite Web services

Algorithm CompositionsConstructionINPUT: G = (X , V ): compositiongraph

P = P1, P2, · · · , Pn: providersOUTPUT: C: potential compositionsT ← Construct −Tree( X , P)t ← 1WHILE t <=

Qni=1 |Pi |

Xt ← ElementaryPath( T )//Xt = s·1, s·2, · · · , s·nFOR each (Sh, Sk ) ∈ V

Vt ← (s·h, s·k )END−FOR

ct ← Gt = (Xt , Vt )C ← C ∪ ctt ← t + 1END−WHILE

r

. . .

. . .

. . .

. . .

s11 s2

1 s31

s41

s12 s2

2 s32

s32s2

2s12

s13 s2

3 s13

s23

s14

s14

s15 s2

5 s35 s4

5 s55

s15 s2

5 s35 s4

5s5

5

s16 s2

6s1

6 s26

. . .

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Potential composite Web services

Algorithm CompositionsConstructionINPUT: G = (X , V ): compositiongraph

P = P1, P2, · · · , Pn: providersOUTPUT: C: potential compositionsT ← Construct −Tree( X , P)t ← 1WHILE t <=

Qni=1 |Pi |

Xt ← ElementaryPath( T )//Xt = s·1, s·2, · · · , s·nFOR each (Sh, Sk ) ∈ V

Vt ← (s·h, s·k )END−FOR

ct ← Gt = (Xt , Vt )C ← C ∪ ctt ← t + 1END−WHILE

r

. . .

. . .

. . .

. . .

s11 s2

1 s31

s41

s12 s2

2 s32

s32s2

2s12

s13 s2

3 s13

s23

s14

s14

s15 s2

5 s35 s4

5 s55

s15 s2

5 s35 s4

5s5

5

s16 s2

6s1

6 s26

. . .

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Evaluation of compositions

General formula:

vj(x) = Φj [gj(x),Ω(Γ+(x)) (1)

Response time:

v1(x) = gj(x) + maxv1(y) : y ∈ Γ+(x) (2)

or

v1(x) = gj(x) +∑

y∈Γ+(x)

π(x , y) · v1(y) (3)

Security

v4(x) = mingj(x), miny∈Γ+(x)

v4(y) (4)

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Evaluation of compositions

s

s

s

s

s

s

1

2

3

4

5

6

P

P

1

2

Composition graph

flow

switch join

s

s

s

s

s

s

1

2

3

4

5

6

P

P

1

2

C1

2

2

1

4

2

3

s

s

s

s

s

s

1

2

3

4

5

6

P

P

1

2

C1

3

2

2

3

2

2

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Evaluation of compositions

Response time of composite Web service:

s

s

s

s

s

s

1

2

3

4

5

6

P

P

1

2

flow

switch join

2

2

1

4

2

3

2

2

4

3

1

2

V( )=2s63

bottom − up algorithm

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Evaluation of compositions

Response time of composite Web service:

s

s

s

s

s

s

1

2

3

4

5

6

P

P

1

2

flow

switch join

2

2

1

4

2

3

2

2

4

3

1

2

V( )=2

V( )=6

s63

s52

bottom − up algorithmDecision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Evaluation of compositions

Response time of composite Web service:

s

s

s

s

s

s

1

2

3

4

5

6

P

P

1

2

flow

switch join

2

2

1

4

2

3

2

2

4

3

1

2

V( )=2

V( )=6

V( )=4

s63

s52

s 44

bottom − up algorithmDecision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Evaluation of compositions

Response time of composite Web service:

s

s

s

s

s

s

1

2

3

4

5

6

P

P

1

2

flow

switch join

2

2

1

4

2

3

2

2

4

3

1

2

V( )=2

V( )=6

V( )=4

V( )= 5

s63

s52

s 4

s

4

13

bottom − up algorithmDecision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Evaluation of compositions

Response time of composite Web service:

s

s

s

s

s

s

1

2

3

4

5

6

P

P

1

2

flow

switch join

2

2

1

4

2

3

2

2

4

3

1

2

V( )=2

V( )=6

V( )=4

V( )=5

s63

s52

s 4

s

V( )=3

s

4

13

22

bottom − up algorithmDecision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Evaluation of compositions

Response time of composite Web service:

s

s

s

s

s

s

1

2

3

4

5

6

P

P

1

2

flow

switch join

2

2

1

4

2

3

2

2

4

3

1

2

V( )=2

V( )=6

V( )=4

V( )=5

s63

s52

s 4

s

V( )=

V( )=7

s 3

s 2

4

13

22

1

bottom − up algorithmDecision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Conclusion

Proposed model

General framework to composite Web services using QoS

Multicriteria evaluation based approach

QoS criterion evaluation

Generate the different potentials compositions

Futur research

Finalization of the being developed prototype

Extension for the framework to support dynamiccomposition (composition graph)

Quantitatives criteria: random variables (response time,availability,...)

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection

Web service architectureWeb services selection

Proposed modelConclusion

Second Workshop Decision Deck

Area: Web servicesTopic: Performance evaluation of Web servicesLaboratory: Lamsade (Paris-Dauphine)Home page: http://www.lamsade.dauphine.fr/∼youcef

Thank you for your attention !

Decision Deck, February 21-02-2008 Multicriteria Framework for Composite Web Selection