Dependability Modeling

Introduction

Due to ubiquitous provision of services on the Internet, dependability has become an attribute of prime concern in hardware/software development, deployment, and operation. Providing fault tolerant services is inherently related to adoption of redundancy. Redundancy can be exploited either in time or in space. Replication of services is usually provided through distributed hosts across the world, so that whenever the service, the underlying host or network fails, another service is ready to take over (Gorbenko, A., Kharchenko, A., Romanovsky, A. 2007). Dependability of a system can be understood as the ability to deliver a specified functionality that can be justifiably trusted (Laprie, J. C. 1992). Functionality might be a set of roles or services (functions) observed by an outside agent (a human being, another system etc) that interacts with system at its interfaces; and the specified functionality of a system is what the system is intended for. This chapter aims to provide an overview of dependability modeling. The chapter starts briefly describing some early and seminal work, their motivations and the succeeding advances. Afterwards, a set of fundamental concepts and definitions are introduced. Subsequently, the modeling techniques are classified, defined and introduced as well as a representative set of evaluation methods is presented. Later on, case studies are discussed, modeled and evaluated.