Dependability Assessment of Service-Oriented Architectures Using Fault Injection

Dependability Assessment of Service-Oriented Architectures Using Fault Injection

Nik Looker (Durham University, UK) and Malcolm Munro (Durham University, UK)
DOI: 10.4018/978-1-60960-493-6.ch016
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Abstract

Dependability assessment is an important aspect of any software system and shows the degree of trust and quality of service that is delivered by a system. Validation and verification techniques commonly employed to ensure that systems are fit for use attempt to remove all faults so that error conditions cannot occur but since it is not feasible to verify all states a system can achieve, it is not possible to completely test a system. Conversely, dependability assumes that failures may occur in a system and that mechanisms exist to mitigate any failures and thus provide a trustworthy system. This chapter discusses the different issues associated with dependability. The different techniques that can be used to assess dependability are discussed and are related to Service Orientated Architectures. A number of cases studies are used to show the practicality of the techniques used.
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Introduction

Dependability (Avizienis, Laprie, Randell & Landwehr, 2004) is a discipline that provides an assessment of how much trust can be placed on a system to deliver a Quality of Service (QoS). Systems need not be fault free but should deliver their functionality when required. This is because it is virtually impossible to engineer a system that can be guaranteed to be fault free; so dependability assumes that faults exist in a system but mechanisms exist to either eliminate them or tolerate their presence. In either case a dependable system will perform its intended function. Validation and verification techniques, on the other hand, attempt to determine that a system contains no faults. This is an important discipline and increases the overall reliability of a system but is difficult to achieve with current techniques. Dependability is a more realistic approach since it measures the reliance that can be placed upon a system rather than validating it against its specification and includes methods that increase this.

This paper provides a review of dependability and some useful fault injection based assessment techniques that can be applied to web services that implemented a Service-Oriented Architecture (SOA). We present a number of case studies, based on some of our previous work, to demonstrate how these assessment techniques can be applied.

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