[email protected] Laboratoire d'InfoRmatique en Image et Systèmes d'information UMR 5205 1 July 2010 2010 Selecting Web Services

[email protected]

Laboratoire d'InfoRmatique en Image et Systèmes d'informationhttp://liris.cnrs.fr

UMR 5205

1 July 2010

2010

Selecting Web Services for Choreography Implementation: Compatibility Checking

Approach with Access Control

Emad Elabd , Emmanuel Coquery, Mohand-Said Hacid

Seke- 1-3 July, 2010

Agenda:

Web Services and Web Services Choreography

Business Protocol

Compatibility

Business Protocols for Choreography

BP Product Automata

Using ontology

The verification process

Complexity analysis

Related works

Conclusion and future work

Seke- 1-3 July, 2010 2

Web Services

3Seke- 1-3 July, 2010

``A Web service is a software application or component that can be accessed over the internet using a platform/language-neutral data interchange format to invoke the service and supply the response, using a rigorously defined message exchange pattern, and producing a result that is sufficiently well-defined to be processed by a software application. ’’

Web service characteristics:

Interactions: XML message

exchange

Protocols: SOAP, HTTP

Service Registry

Service Provider

Service Requestor

Service description

Web Service

Service-oriented architectures (SOA).

Web Services cont.

4

Structural Behavioural

Tools:WSDLTools:WSDLTools: BPEL, WSCI, BPMN,

etc.

Tools: BPEL, WSCI, BPMN,

etc.


Service Description

Operations, data schemas, binding

information and I/O messages format

Operations, data schemas, binding

information and I/O messages format

Order of messages exchange(Business

protocols)

Order of messages exchange(Business

protocols)

Web Services & Choreography

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WA2

WAn

WA3

WA1

WA4

WEB

Web Services

Designer

.

.

.

Collects

Implements

Complex process Selected Web services

Described by

Verification

Process choreography

Can implement process or not

Informal definition: Possible message exchange sequences supported by the service.Informal definition: Possible message exchange sequences supported by the service.

6

Business Protocol

Formal definition :An explicitly time business protocol is a tuple P = (S; s0; T; F) which consists of the following elements:

– S is a finite set of states.– s0 S, is the initial state.∈– T S⊆ 2xM x{+,-} , is a finite set of explicit transition.– This protocol is deterministic.– All states in the automata are accessible and co-accessible.– F S is a set of final states. If F = { } then P is said to be an empty ⊆ ∅protocol.

Formal definition :An explicitly time business protocol is a tuple P = (S; s0; T; F) which consists of the following elements:

– S is a finite set of states.– s0 S, is the initial state.∈– T S⊆ 2xM x{+,-} , is a finite set of explicit transition.– This protocol is deterministic.– All states in the automata are accessible and co-accessible.– F S is a set of final states. If F = { } then P is said to be an empty ⊆ ∅protocol.


7

Business Protocol cont.

a(-) d(+) e(+)S0 S1 S2 S4

S4

start Logged searching answeredansweredLogin(+) search(+)

search(+)

answer(-)

business protocol of a search engine.

p1

p2

State transition protocol of a search engine.


Compatibility

Seke- 1-3 July, 2010 8

Service Consumer

Business Protocol

Business Protocol

specifyspecifyDescribed by Described by

Service Provider

Compatibles?

interactions messagesmessages

Compatibility

Seke- 1-3 July, 2010 9

Informal definition. we say that P1 and P2 are compatible using their

if:

• All the messages get out from the service can be received

from the consumer and vice versa with respecting the

annotated constraints ( time and ACP).

• There are no life or dead lock( accessibility and co-

accessibility)

Informal definition. we say that P1 and P2 are compatible using their

if:

• All the messages get out from the service can be received

from the consumer and vice versa with respecting the

annotated constraints ( time and ACP).

• There are no life or dead lock( accessibility and co-

accessibility)

Compatibility ex.

10

b(+)

a(+) d(-)

a(-) d(+)

c(-)

a�

d

BP1

BP2

Two BP their product automata.

S0 S5S5

S2

S1

S’0 S’1

(S0,S’0) (S1,S’1)

S’5S’5

(S5,S’5)(S5,S’5)

BP1 × BP2

S3S4

e(+) f(-)

S’3 S’4

e(-) f(+)

(S3,S’3) (S4,S’4)e�

f

p1

p2

P1 X P2


Incompatible ex.

11

b(-)

a(+) d(-)

a(-) d(+)

c(+)

a�

d

BP1

BP2

The two protocols are incompatible

S0 S5S5

S2

S1

S’0 S’1

(S0,S’0) (S1,S’1)

S’5S’5

(S5,S’5)(S5,S’5)

BP1 × BP2

S3S4

e(+) f(-)

S’3 S’4

e(-) f(+)

(S3,S’3) (S4,S’4)e�

f


Web Services: Access control

12

Development of suitable access control models

Traditional access control models are not satisfactory :

Conversational nature of Web services.

Web service as a set of dependent operations.

Approaches to avoid situations where the client cannot progress in the conversation due to the lack

of required security requirements.

Research directions in access control. (

Development of new access control models (e.g, NIST Standard RBAC model WS-AC1, and

conversation-based Web services access control model by Massimo M. et al.

Development of policy languages for access control( XACML , WS-Policy and finally to

Semantic Web based languages such as Rei and KAoS.


Compatibility with AC:

Seke- 1-3 July, 2010 13

- For login: professor credential or student card-For accessing journal papers: professor credential-For access conference papers: professor credential or student card

Business protocol of the web service (P1) and a consumer (P2) without assigning the ACP.

start Logged

ReceivedJournalReq JournalPapersJournalPapers

Login(+)getJournalReq(+)

conferPapersconferPapers

getconferenceReq(+)

ReceivedconfReq

getJournalRes(-)

getconfRes(-)

start Logged SentRequest GetJournalPaperGetJournalPaperLogin(-)

getJournalReq(-)getJournalRes(-)

P1

P2

Compatibility with AC cont.:

Seke- 1-3 July, 2010 14

Business protocol of the web service (P1) and a consumer (P2) after assigning the ACP.

start Logged

ReceivedJournalReq JournalPapersJournalPapers

Login(+),Prof orStudent

getJournalReq(+),Prof

conferPapersconferPapersgetconferenceReq(+) Prof orStudent

ReceivedconfReq

getJournalRes(-)

getconfRes(-)

start Logged SentRequest GetJournalPaperGetJournalPaperLogin(-)

,Student

getJournalReq(-)getJournalRes(-)

P1

P2


15

M3(-)M1(-),C M2(+) M4(+)S0 S1

S2 S3 S4S4

C:is a credential or a set of credentials.M : refers to the message

P1

M3(+,C)M1(+) M2(-) M4(+)S’0 S’1

S’2 S’3 S’4S’4

P2

M3(-),CM1(-),C M2(+) M4(+)S0 S1

S2 S3 S4S4

P1 with cumulative ACP

M3(+,C)M1(+) M2(-) M4(+)S’0 S’1

S’2 S’3 S’4S’4

P2

Cumulative Access control policy



16

M7(-), zxor yz

M1(-),x M3(+) M8(+)S0 S1 S2 S3 S4

S4

S5 S6 S7

P1

M2(-)M4(+) M5(-),y

M6(+)

M7(+), zxor yz

M1(+) M3(-) M8(-)S0 S1 S2 S3 S4

S4

S5 S6 S7

M2(+)M4(-) M5(+)

M6(-)

M7(+),xzM1(+) M3(-) M8(-)S0 S1 S2 S3 S4

S4

S5 S6 S7

M2(+)M4(-) M5(+)

M6(-)

P2

P3

Policy Compatible

Compatible? Answer :No



17

M7(-), zxor yz

M1(-),x M3(+) M8(+)S0 S1 S2 S3 S4

S4

S5 S6 S7

P1

M2(+)M4(+) M5(-),y

M6(+)

M7(+), zxM1(+) M3(-) M8(-)S0 S1 S2 S3 S4

S4

P2

Are the two protocol compatibles?• by applying the rule of the previous example it seems NO. because in M7 in p2 the policy will not satisfied by the set of credentials of M7 in p1.• But they are compatible.

•Some paths will not be taken during the interaction.•Compare the credentials and policy after determining the paths of interaction between the two protocols(product automata)

Policy


Access Control Policy cont.:

18

b(-)

a(+), (c1) d(-),c2

a(-), c1 d(+)

c(+)

, P11 =c1, c1

2 =c1

, P22 =0, c2

1 =c2a� d

BP1

BP2

Two BP assigned with access control policy and their product automata.•P1

1 policy of protocol BP1 in transition 1•C1

2 set credentials of protocol BP2 in transition 1

S0 S5S5

S2

S1

S’0 S’1

(S0,S’0) (S1,S’1)

S’5S’5

(S5,S’5)(S5,S’5)

BP1 × BP2

S3S4

e(+) f(-)

S’3 S’4

e(-) f(+),c2,c3

(S3,S’3) (S4,S’4)

e� f

P42 =c2c3, c4

1 =0

P31 =0, c3

2 =0

Example of incompatibility

C41 =c2C3

2 =c1C21 =c2C1

2 =c1


Web Service Choreography

19

•Web service choreography relates to describing externally observable interactions between web services•Choreography == Multi-party Collaboration

(Seller, Broker, SubmitArticleSpec, AritclesubmitReq, ACP=true, C=true)

(Broker, Seller, QuoteUpdate,QuoteUpdateReq, ACP=true, C=true)

(Seller, Broker, QuoteUpdate,QuoteUpdateRes, ACP=true, C=true)

START((Buyer, start),(Seller, start),(Broker,start),(CreditAgency,start)))

ARTICLE SPECIFIATION SUBMIT ((Buyer, start),(Seller,

Sent_Req),(Broker,Rec_Req),(CreditAgency,start)))

QUOTE UPDATING REQUEST-KS ((Buyer, start),(Seller,

Rec_QU),(Broker,Sent_QU),(CreditAgency,start)))

QUOTE UPDATING RESPONSE-SK((Buyer, start),(Seller,

Sent_QU),(Broker,Rec_QU),(CreditAgency,start)))


Partners

Sender

Reciever

Operation

Message

ACP

Credentials


Business Protocols for Choreography

20

AritcleQuoteRequest(-),

Broker PayementOrder(-) ,LCL Master Card,

Broker

AritcleQuoteResponse(+),

Broker

QuoteUpdateReq(-),Broker

Getarticle(+),Broker

ArticleAccessed

ArticleDenied

Cancel(+),Broker

Start

AritcleQuoteRequest(+),

buyerPayementOrder(+) ,Credit Card, buyer

AritcleQuoteResponse(-),

buyer

ArticleAccessed(-),buyer

ArticleDenied

Cancel(-) ,buyer

BUYER

SELLER

AritclesubmitReq(-),

Broker

PayementOrder(+),Visa

Card, Broker

AritcleSubmitRes(+),

Broker

Cancel(+),Broker

Start

QuoteUpdateRes(+),,Broker

QuoteUpdateReq(+),buyer

QuoteUpdateRes(-) ,buyer

QuoteUpdateReq(+),Broker

QuoteUpdateRes(-),Broker

BROKER

AritclesubmitReq(+) ,seller

StartAritcleSubmitRes(-),

seller

QuoteUpdateReq(-) ,Seller

QuoteUpdateRes(+),Seller

CreditCheckReq(-),CreditAgency

PayementOrder(-),Visa Card,

Seller

Cancel(+),Seller

ArticleSent(+),Seller

CreditCheckReq(-),

CreditAgency

Accept(-) ,CreditAge

ncy

Failure(+),CreditAgency

Failure(+),CreditAgency

cancel(+),Broker

ArticleSent(-),Broker

Accept(-) ,CreditAgency

CREDITAGENCY

CreditCheckReq(+),(Seller,Boker)

Accept(-),(Seller,Boker)

Failure(-),(Seller,Boker)

Start


Product Automata

21

((Buyer, start),(Seller, start),(Broker,start),(CreditAgency,

start)))

ARTICLE SPECIFIA

TION SUBMIT

(Seller, Broker, SubmitArticleSpec, AritclesubmitReq, ACP=true, C=true) Quote

Updating Request-

KS


…..

Payement Request-

Ks

Payement Check-Sc

(Seller, CreditAgency, checking credit, CreditCheckReq, ACP=Visa

Card, C=BNP Visa Card)

Payement failure-CS

Payement Success-Cs

(CreditAgency, Seller, checking credit, Failure, ACP=true, C=true)

(CreditAgency, Seller, checking credit, Sucess,

ACP=true, C=true)

…Article

recieved

Article Submit

(Broker, Buyer , SubmitArticle, Aritclesubmitorder, ACP=true,

C=true)


Access control policy ontology

22

start Logged

ReceivedJournalReq

JournalPapersJournalPapers

Login(+),Prof or

Student card

getJournalReq(+),Prof

conferPapersconferPapers

getconferenceReq(+)Prof orStudent

ReceivedconfReq

getJournalRes(-)

getconfRes(-)

start Logged SentRequest GetconfPaperGetconfPaperLogin(-) ,school Student getconferenceReq(-)

getconfRes(-)

P1

P2

Card

Student card Professor card

University cardSchool card

Isa Isa

IsaIsa

Ontology


The verification process

23

1.Select the Web services and get its business protocols assigned with the ACP and

credentials.

2.Create the product automata between these protocols.

3. Calculate the cumulative ACC on the product automata (as defined on definition 4).

4.Check the compatibility in terms of ACP between these protocols (as defined on

definition 6) using algorithm 1 for calculating and checking the ACP on the product

automata.

5. If the business protocols are compatible in terms of message exchange and ACP and the

product automata presents the same behavior as the choreography then the set of

services which have these business protocols can implement this choreography.

Otherwise, this choreography cannot be implemented by these ser-vices.


Complexity analysis

24

Complexity analysis: Let T1 and T2 be the number of transitions of the

two protocols P1 and P2 respectively,

-The construction of the product automata will take (T1 xT1).

-The calculation of the cumulative credentials will take number of

states in the product automata (S1 x S2) multiplied by the size of the

longest non looping path multiplied by (S1 S2) (i.e cumulative

credentials takes(S1 x S2)3)

-As a result, the complexity for the algorithm will be ((T1 xT1) + (S1

S2)3).

Complexity analysis: Let T1 and T2 be the number of transitions of the

two protocols P1 and P2 respectively,

-The construction of the product automata will take (T1 xT1).

-The calculation of the cumulative credentials will take number of

states in the product automata (S1 x S2) multiplied by the size of the

longest non looping path multiplied by (S1 S2) (i.e cumulative

credentials takes(S1 x S2)3)

-As a result, the complexity for the algorithm will be ((T1 xT1) + (S1

S2)3).



High-level analysis of business protocols used in the web service after

explicitly assigning ACP on it .

• Cumulative access control Policy

• Compatibility analysis

Propose a verification approach to verify the behaviors specified by

processes choreographies and the selected web services for implementing

these choreographies.

In our work, using ontology of ACP is important in determining the

relation between the compared policies and credentials . This comparison

is needed in checking the compatibility and replaceability.

25Seke- 1-3 July, 2010


For future work

• Generalization approach works with most of message specification

attributes (XMLSchema, Access Control Policy, Privacy, Meaning,

Response Time, Credentials).

• Applying our analysis on multi-clock time automata where each

transition has its own clock.

• automatically build adapters allowing set of services to work

together even though they are not directly compatible

• Another extension is to use these tools for web service composition

26Seke- 1-3 July, 2010

Documents

[email protected] Laboratoire d'InfoRmatique en Image et Systèmes d'information UMR 5205 1 July 2010 2010 Selecting Web Services