Failure Recovery of Composite Semantic Web Services

using Subgraph Replacement

Hadi Saboohi

Amineh Amini

Hassan Abolhassani

Karaj Islamic Azad University, IRAN

Web Services

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A software system designed to support interoperable Machine to Machine interaction over a network

Web APIs

Semantic Web

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Extension of current web Giving well-defined meaning to information Enabling computers and people to work in

cooperation

Semantic Web Services

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Semantically marked-up software resources that can be published, discovered, composed and executed across the Web in a task driven semi-automatic way

Dynamic part of the semantic web

Semantic Web Services, continued

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InteroperableSyntax

InteroperableSemantics

DynamicResources

StaticResources

Web Services

WWW

Semantic Web Services

Semantic Web

Service Broker

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Service Broker

Service Registry

Concepts Registry

Ontology Cache

Composed ServicesCache

Registry Manager

Ontology Manager

ComposerAdapterMatchmaker

ExecutorKernel

Ref. 4

Modeling Composite Semantic Web Services

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Directed Acyclic Graph Nodes: Web Services Edges: Services inputs and outputs

1)()( GEGV

I, PA Si B

O, E

OA, EA

ISi, PSi

OSi, ESi

IB, PB

Execution problem of a composite semantic web service

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Execution of whole process depends on well-execution of all sub-processes

In execution failure of any constitutive web service, failure recovery is a better solution

Our approach Replace a sequence of web services containing

failed service in case a “same skilled” one is not exists

Replacement Strategy

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Responsible for: Finding best substitution alternative Managing differences between old and new

service(s)

Replacement Steps

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1. Finding all possible alternatives a. Subgraph calculationb. Alternative search

2. Ranking alternatives3. Replacement

1. a. Subgraph calculation

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A S B

A S B

A S

A

S B

S

B

Composite Graph

All possible subgraphs

1. b. Alternative search

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Search for compatible replacement alternatives

Compatibility Functional attributes (Inputs, Outputs, Effects and

Preconditions) Non-functional

Response time Availability Reliabiity Cost …

2. Ranking alternatives

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Each constitutive web service may exist in more than one subgraph For example: S is in four subsets of subgraphs

({S}, {A,S}, {S,B}, {A,S,B}) Each subgraph may have several alternatives

esδDifferencNewβNewβ

UndoαUndoαRank

Cost2Length1

Cost2Count1

3. Replacement

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First: re-execution attempts Second: Replacing best ranked subgraph

Compensation of well-executed web services in old subgraph

Replacement Patterns

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Managing differences between old and new subgraphs

New subgraph may have additional IOPE(s) than old one and vice versa Prepare required inputs and preconditions Mark the composite as non-optimized and inspect

to execute without additional outputs and effects

Conclusion and Future Works

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Alleviate failure of software systems (CSWS) Replacing a sequence of web services Using forward and backward mechanisms Heuristic algorithms to decrease number of

subgraphs Extend for all composition graphs