Thesis Report:Thesis Report:Composition and Composition and

Evaluation ofEvaluation ofTrustworthyTrustworthy

Web ServicesWeb Services

Thesis Report:Thesis Report:Composition and Composition and

Evaluation ofEvaluation ofTrustworthyTrustworthy

Web ServicesWeb Services

James S.F. Hsieh, nomad_libral@gmail.comSOA Team, KS Lib,

Graduate Institute of Network Learning Technology, National Central University, Taiwan

Outline Introduction Motivation Our Proposed Architecture

Part 1: Single Service Trustworthy Evaluation– Specifications of Trustworthy Experience– Trustworthy Requirement Matching– Requirement Hypothesis and Confidence

Part 2: Composite Service Trustworthy Evaluation– Composition Confidence– Trustworthy Web Service Evaluation Petri Net– Composition Confidence Evaluation– Evaluation Algorithm

Conclusion References

IntroductionSOA could

– seamlessly integrate existing services to fulfill dynamic requests in distributed platforms and

– promise that service providers will offer the functionality to service requesters without exposing details of provided services.

The web service exists a big problem: trustworthiness problem.

The trustworthiness solution was separated into following:1. Infrastructure

For example: XML Signature, XML Encryption, and P3P projects…(W3C)

2. Understanding– Abstract Behavior Model– Past Experiences Analysis

For example: Rating Service, Reputation Mechanism, and Referral Network…

3. Policy

Motivation (1/2)What is our motivation: (specify, evolve and use trust)

Important problems are

1. how do we utilize past experiences to evaluate a service and

2. how to utilize past experiences to compose a composite web service from a lot of sub-services. (dynamic composite)

We will solve the following problems:

How do we evaluate trust of a signal web service (atomic service or simple service)? The evaluation should be a formal method.

How do we consider structure of a composite web service while we evaluate trust of it? We need a formal model to specify the structure.

Motivation (2/2)Define: I defined trust between requester and provider is that anything of suitable trustworthy requirement which be defined formally and specifically by service requester and be measured objectively and quantitatively by agreed suitable third-party is performed completely by service provider.

1. Expectation-phase2. Contract-phase

Step 1. Propose a requirement

Step 2. Analyze requirement and compose a composition

web service

Step 3. Perform services

Step 4.Composition service

is consumed by requester

Step 5. Feedback

Step 6. Experience is published

Trustworthy Experience

Trustworthy Requirement

Service Instances

Expectation-phase

Contract-phase

Our Proposed Architecture (1/2)

Based on CMU Framework

Evaluate trust of a signal web service.

Evaluate trust of a composite web service.

Our Proposed Architecture (2/2)

Ontologies of Trust General

Aspects

Ontologies of Trust Domain

Aspects

Trustworthy Experience

Trustworthy Requirement

Requester

Service InstancesMapping

Step 4. Composition service is consumed by requester

Step 5. Feedback Step 6. Experience is published

Schedules

Sub-Service Confidences

Composite Confidences

Communication

Objective Task Plans

Reputation or Social Network

UDDI

Result

Service Provider

Composition Flow

Composition Data Flow

Trustworthy Evaluation Data Flow

Service Composition Module

Trustworthy Evaluation Module

Scheduler

Evaluation

Execution

Choice

Planner

InquiryStep 1. Propose a

requirement

Step 3. Perform services

Step 2. Analyze requirement and

compose a composition web service

Trust Management Cycle

Part 1: Single Part 1: Single Service Trustworthy Service Trustworthy

EvaluationEvaluation

Part 1: Single Part 1: Single Service Trustworthy Service Trustworthy

EvaluationEvaluation

Specifications of Trustworthy Experience

Trustworthy Requirement Matching Requirement Hypothesis and

Confidence

Specifications of Trustworthy Experience (1/3)

Description of trustworthy experience of bookstore services

General aspect

Functional 1.Does requester’s goal regarding this service request has been fulfilled?

Non-Functional

Network performance

1.What is the response time of service in this service?2.What is the turnaround time of service in this service?3.What is the packet miss rate of service in this service?

Security 1.Does the service use RSA technology?2.Does the service use DES technology?

Domain aspect

Selling

Bookstore 1.How long will it take to deliver the requested book in this service?2.Does the book have been damaged during delivery in this service?3.What is the list price of the requested book in this service?

Specifications of Trustworthy Experience (2/3)

-Response time-Throughput-Turnaround time-Packet miss rate-......

Network performance -Book delivery time-Book price-Book damage-......

Bookstore

-Service provider-Service requester-Time stamp-.....

Trustworthy Experience

General aspect Domain aspect1*

1 *

-Reach-.....

Functional

-.....

Security

Non-Functional

-Behind schedule-Fare price-Accident-No seat-......

Airways

Selling Domain XBooking

……

-.....

Aspect X

……

An example of the trustworthy aspect ontology

Specifications of Trustworthy Experience (2/3)

Description of an experience instance for bookstore service

AspectProperty Value

Functional Reach True

Network performance

Response timeTurnaround timePacket miss rate

510 ms2100 ms1.5 %

Security RSA technologyDES technology

TrueTrue

Bookstore Book delivery timeDamagePrice

2 Days 3 HoursFalse$ 53.5

tr

Step 1. Propose a requirement

Step 2. Analyze requirement and compose a composition

web service

Step 3. Perform services

Step 4.Composition service

is consumed by requester

Step 5. Feedback

Step 6. Experience is published

Trustworthy Experience

Trustworthy Requirement

Service Instances

Trustworthy Requirement Matching

Tr

SE \1s2s3s4s5s256s 1tr2tr10tr

Trustworthy requirements are kind of rule based policies that I can utilize to determine whether described trustworthy experiences are acceptable and meet service requester’s trustworthy requirement. Trustworthy requirements are similar to sentences appeared in propositional logic.

2% rate, miss e.Packetperformanc Networkr Smalle

DamageBookstore. technology SASecurity.R.ReachFunctionalAccept :S

$50 Price,Bookstore. SmallerDays 2 time,delivery BookBookstore.r Smalle

700ms time, e.Responseperformanc NetworkSmaller.ReachFunctionalAccept :S

2

1

　

　

tr KB,ASK

SKB,TELL , SKB,TELL 21

Step 1. Propose a requirement

Step 2. Analyze requirement and compose a composition

web service

Step 3. Perform services

Step 4.Composition service

is consumed by requester

Step 5. Feedback

Step 6. Experience is published

Trustworthy Experience

Trustworthy Requirement

Service Instances0

Requirement Hypothesis and Confidence Requirement Hypothesis - We can utilize the ontology instance to

specify a trust requirement of a requester.

Confidence - We utilize “Large-Sample of Hypothesis for a Binomial Proportion” to evaluate the simple error and true error of

the hypothesis.

Tr

SE \1s2s3s4s5s256s 1tr2tr10tr

otherwise0

Accept tr KB,ASK1trAccpet

S∈s

sRatingAccpetn

=p )(1

ˆ

n

ppSD

ˆ1ˆ

961z95 .%

0 ,ˆmax %95 SDzpConfidence

,

,

Part 2: Composite Part 2: Composite Service Trustworthy Service Trustworthy

EvaluationEvaluation

Part 2: Composite Part 2: Composite Service Trustworthy Service Trustworthy

EvaluationEvaluation Composition Confidence Trustworthy Web Service

Evaluation Petri Net Composition Confidence

Evaluation Evaluation Algorithm

In the OWL-S description language, the schedule of a service has control structures which similar to the following structures . We can compose separate Confidence to a Composition Confidence.

Composition Confidence

Composition Confidence

Tr

SE \1s2s3s4s5s256s 1tr2tr10tr

Sub-service 1 Sub-service 2

confidence1 confidence2

Sequence Pattern

Concurrent Pattern

confidence of the composite service = confidence1 × confidence1

Sub-service 1

Sub-service 2

confidence1

confidence2

Switch and IF-Then-Else Pattern

Sub-service 1

Sub-service 2

confidence1

confidence2

confidence of the composite service =min{ confidence1 , confidence1 }

Trustworthy Web ServiceEvaluation Petri Net (1/3)We proposed the Trustworthy Web Service Evaluation Petri Net to specify structure of a OWL-S in following.

is a finite set of places, each place represents a control-structure.

is a finite set of transitions, each transition represents a sub-service.

is a finite set of transitions, each transition represents a schedule-control.

is a set of arcs, each arc represent the control flow between sub-service.

is a set of all sub-services.

is a mapping function, it maps the transitions of the Petri nets to the sub-services of a composite web service.

is a mapping function, it maps the sub-services to these confidences, and we can use the Requirement Hypothesis to compute the of sub-services

Trustworthy Web ServiceEvaluation Petri Net (2/3)

Sequence

Split

Start(Split)

Split-Join

Start(Split-Join) Finish(Split-Join)

IF-Then-Else

Repeat-Until

Start(Repeat-Until) Finish(Repeat-Until)

Iterate(Repeat-Until)

A control flow of a general composite service can be organized by the following control patterns.

Trustworthy Web ServiceEvaluation Petri Net (3/3)<process:CompositeProcess rdf:ID="CompositionService">

<process:composedOf>

<process:If-Then-Else>

<process:ifCondition>…</process:ifCondition>

<process:then>…

<process:AtomicProcess rdf:about="#Ser1"/>

</process:then>

<process:else>…

<process:SplitJoin>…

<process:AtomicProcess rdf:about="#Ser2"/>

<process:Repeat-Until>

<process:untilCondition>…</process:untilCondition>

<process:untilProcess>…

<process:AtomicProcess rdf:about="# Ser3"/>

</process:untilProcess>

</process:Repeat-Until>

</process:SplitJoin>

</process:else>

</process:If-Then-Else>

</process:composedOf>

</process:CompositeProcess>

For Example: OWL-S

[1,0,0,0,0,0,0,0]

[0,1,0,1,0,0,0,0]

[0,0,1,1,0,0,0,0]

1t̂

4t

[0,0,1,0,1,0,0,0]5t̂

[0,0,1,0,0,1,0,0]7t

[0,0,1,0,0,0,1,0]

8t̂

[0,0,0,0,0,0,0,1]

2t̂

6t̂

[0,1,0,0,1,0,0,0]5t̂

[0,1,0,0,0,1,0,0]

7t4t

4t

6t̂

3t

Minitial

Mfinal

M1

M2

M3

M4

M5

M6

M7Each edge has a Confidence value ina Coverability Graph.

The Coverability Graph is a special case of the Markov Process.

Composition ConfidenceEvaluation (1/2) As we evaluate the Composite Confidence of a TWSEPN we must

find out the minimum confidence product of the firing sequences between the Minitial and Mfinal the in the Coverability Graph.

Case 1: If coverability graph is a directed acyclic graph,

we propose a algorithm which is based on the AOE and the BFS to calculate the Composite Confidence.

Case 2: Otherwise,we find the Strongly Connected Components out, and we compress that into two vertexes and one edge so the directed graph can be converted to a DAG (Case 1).

Composition ConfidenceEvaluation (2/2)For Example: The following is a directed graph which exists cycle.

[1,0,0,0,0,0,0,0]

[0,1,0,1,0,0,0,0]

[0,0,1,1,0,0,0,0]

1t̂

4t

[0,0,1,0,1,0,0,0]

5t̂

[0,0,1,0,0,1,0,0]

7t

[0,0,1,0,0,0,1,0]

8t̂

[0,0,0,0,0,0,0,1]

2t̂

6t̂

[0,1,0,0,1,0,0,0]5t̂

[0,1,0,0,0,1,0,0]

7t4t

4t

6t̂

3t

Minitial

Mfinal

M1

M2

M3

M4

M5

M6

M7

Compress the cycle into case 1.Case 2

Case 1

SCC

Evaluation Algorithm

Case 1

[Minitial, M1, M2, M34, M34’, M5, M67, M67’, Mfinal ]

Step 1 [1, 1, 1, 1, 1, 1, 1, 1, a]1Step 2 [1, 1, 1, 1, 1, 1, 1, 1, a]

2

3Step 3 [1, 1, b, 1, 1, 1, 1, 1, a]

4Step 4 [1, 1, b, b, 1, 1, 1, 1, a]

5Step 5 [1, 1, b, b, 1, 1, cδ, 1, a]

6Step 6 [1, 1, b, b, b×cδ, 1, cδ, 1, a]

7Step 7 [1, 1, b, b, b×cδ, 1, b×cδ, 1, a]

8

Step 8 [1, 1, b, b, b×cδ, 1, b×cδ, 1, a]

9

Step 9 [1, 1, b, b, b×cδ, 1, b×cδ, 1,

min{a, b×cδ}]

Composition Confidence = min{a, b × cδ}

Conclusion

Trust is one of the most important issues of SOA. The composite web service composes individual sub-services to reach requester‘s objective. Our proposition bases on the understanding which is nature of trust, to analyze the past experience.

– The Inquiry module use statistics to evaluate the Confidence of the individual sub-service according to the trust requirement.

– The Evaluate module use TWSEPN to model the schedule of the Composite Web Service, and it analyzes Coverability Graph which is deduced from TWSEPN to evaluate the Composite Confidence.

– In the last, the Choice module import policies to decide the best plan and the best schedule of the composite web service and perform that.

The EndThe EndThanksThanks

The EndThe EndThanksThanks

James S.F. Hsieh, nomad_libral@gmail.comSOA Team, KS Lib,

Graduate Institute of Network Learning Technology, National Central University, Taiwan