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Dependable Web Service Compositions usng a Semantic Replication Scheme. LABORATÓRIO DE SISTEMAS DISTRIBUÍDOS – LASID DEPARTAMENTO DE CIÊNCIA DA COMPUTAÇÃO - DCC UNIVERSIDADE FEDERAL DA BAHIA - UFBA. Daniela Barreiro Claro 1. Raimundo José de Araújo Macêdo 2. SBRC 2008.

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Dependable Web Service Compositions usng a Semantic Replication Scheme

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Dependable Web Service Compositions usng a Semantic Replication Scheme

LABORATÓRIO DE SISTEMAS DISTRIBUÍDOS – LASID

DEPARTAMENTO DE CIÊNCIA DA COMPUTAÇÃO - DCC

UNIVERSIDADE FEDERAL DA BAHIA - UFBA

Daniela Barreiro Claro1

Raimundo José de Araújo Macêdo2

SBRC 2008

  • Dr. Daniela Barreiro Claro is supported by FAPESB (BOL2071/2006).

  • Prof. Raimundo José de Araujo Macêdo is supported by FAPESB and CNPQ(Edital Universal).


Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

Outline

  • Motivation

  • Dependability requirements for WSC

  • The SAREK approach

  • Experimental tests

  • Performance evaluation

  • Comparison with related work

  • Conclusion and future directions

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

2


Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

Motivation

  • Web services are autonomous applications that can be published, located and invoked over the Internet.

  • Due to their potential for heterogeneous integration, companies are implementing their business as a Web service format.

  • However, a single Web service cannot fulfill a user request and need to be combined.

Web service Composition

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

3


Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

Motivation

  • Whereas WS specifications cover dependable issues, no one handles the problem of dependable and automatic Web service compositions.

  • This raises another problem: a single WS failure, thus the failure of the whole composition.

  • Availability or continuity of service must be taken into account to apply WSC in critical applications.

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

4


Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

Motivation

  • A commonly used technique for improving availability is to replicate services.

  • This work tackles the problem of dependability requirements of WSC, using ontologies to form a set of semantically alike replicas.

  • We propose a framework SAREK where a failure of a primary service can be masked by the execution of another service semantically compatible.

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

5


Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

Required Properties for WSC

  • Some kinds of faults should be treated by a fault tolerant mechanism in order to reach the goal of a WSC.

    • unavailability of a Web service

    • partially operational WS

    • Internet disconnections

  • Some mechanisms have been introduced

    • FT-SOAP, WS-Reliability, WS-Replication, etc

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

6


Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

Required Properties for WSC

  • Data Consistency

    • WSC should guarantee the integrity of data in its execution

  • Computation Availability

    • It is not possible to assume that all WS in a composition are reliable. A WSC should guarantee availability without knowing the reliability level of single WS

  • Scalability

    • WSC ability to handle a growing amount of WS

  • Transparency

    • WS is included and removed from a composition in a transparent way

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

7


Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

The SAREK approach

  • System model and assumptions

    • A set of activities m is the number of activities.

    • A set of services n is the number of services.

    • Candidate services is a subset of Service for a specific activity

    • A composition C is a sequence of activities performed by a set of services

  • WS are implemented as processes

  • Channels are assumed to be reliable

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

8


Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

The SAREK Approach

  • SAREK is a modified and enhanced version of SPOC1

  • SAREK is divided into two modules

    • The Planner Module

      • Aims to automatically determine the activities for a given composition

    • The Executor Module

      • Aims to execute the composition defined by the Planner

    • Both modules are replicated using a passive replication mechanism.

1. Claro D.B, Albers P. And Hao, J-K. A framework for automatic composition of RFQ Web services. In IEEE SCW/ WSCA-ICWS, Salt Lake City, USA. 2007

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

9


Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

10


Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

The Planner Module

  • The Planner is divided into two main phases: Planning and Optimization

  • The Planning phase

    • It uses an AI Planning algorithm based on preconditions and effects

    • Interacts with OPS (an OWL ontology) to discover services

    • Each WS is described using an OWL-S format

    • This phase aims to determine which activity belongs to the composition in order to fulfill the user request

    • It main issue is the set of activities A that can reach the given request

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

11


Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

The Planner Module

  • The Optimization phase

    • Optimizes the combination of WS and activities

    • The values used to optimize are based on estimated values retrieved from each candidate Web service

    • It seems a quotation system

    • Produces a set of semantic similar compositions

    • We used a genetic algorithm called NSGA-II to get the Pareto optimal solutions, i.e. the compositions

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

12


Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

The Executor Module

  • This module executes the composition using the prefix mechanism

  • In order to provide fault tolerance both a transactional approach and a replication mechanism are applied.

    • Semantic replication scheme

    • Transactional Level

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

13


Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

The Executor Module

  • Semantic replication scheme

    • Faulty Web service can be replaced by a semantically similar service (transparency property)

    • Kind of spatial redundancy, because there is a set of compositions that achieve the same goal.

    • The prefix approach increases performance

      • Only the failed partition of the composition is re-executed

        and the prefix . It saves recovery time supposing that the service s3failed.

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

14


Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

The Executor Module

  • Transactional Level

    • Temporal redundancy mechanism, SAREK tries one more time to recover from a possible transient fault

    • If the problem persists, and no other semantic similar composition can be replaced, SAREK roll back the previous executed Web service

      • Using ACID or a compensation technique

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

15


Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

Experimental Tests

  • Case Study

    • SAREK was applied to a bidding process for repairing public buildings.

  • Prototype implementation of SAREK

    • Java 1.5, Apache Tomcat 5.0, Axis 1.3, Jena API 2.3, OWL-S API 1.1.0 and MySQL Database 4.1

    • Experiments were carried out in single computer

      • Inter motherboard Core Duo, processor T2300 1.66 Ghz and 1Gb of RAM.

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

16


Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

Simulated scenario

  • 4 activities

    • supplyWood, supplyConcrete, supplyIron and buildStaircase

  • Each activity can be performed by 2 candidate services

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

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Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

Simulated scenario

  • There is one WSDL operations for execution

    • String executeWS()

  • Results were produced by 2 runs

    • Without failures

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

18


Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

Simulated scenario

  • With failures (services 5, 3, 6 failed)

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

19


Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

Performance Evaluation

  • Each experiment was run 400 times for calculating the average time and standard deviation

  • Two kinds of experiments

    • A composition is fixed

    • A composition is randomly chosen

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

20


Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

Performance Evaluation

  • The overhead caused by faults for an increasing the number of forced Web services failures.

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

21


Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

Related Work

  • Comparison in the light of the required dependability properties for automatic WSC

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

22


Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

Conclusion and future directions

  • Challenges for achieving Dependable Web service compositions

    • Suggesting a set of required dependability properties.

  • To the best of our knowledge, SAREK is the first framework that provides such fault tolerant guarantees in WSC

  • Future works

    • Evaluate the fault tolerant mechanism in real scenarios

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

23


Experimental Tests

Performance Evaluation

Comparison with Related Work

Conclusion

Outline

Motivation

Properties for WSC

SAREK approach

Thank you!

Daniela Barreiro Claro

dclaro@ufba.br

Raimundo Macêdo

macedo@ufba.br

http://www.lasid.ufba.br

LaSiD/DCC/UFBa

Daniela Barreiro Claro Raimundo Macêdo Dependable Web Service Compositions using a

dclaro@ufba.br macedo@ufba.br Semantic Replication Scheme

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