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Challenges for Creating Highly Dependable Service Based Systems

The paradigm shift from traditional on-premise software to a service based model has gained significant momentum in the past decade. One such concept, Software as a Service (SaaS), delivers the functionality of traditional on-premise software as a service over the web. While a defect or a malfunction in a traditional on-premise application may affect a single user, the affected user base in a SaaS application may span the entire group of customers serviced by the provider. The physical disconnect between end users and the SaaS applications puts onus on service providers to deliver highly dependable systems that are available and reliable at all times. In this paper, we explore the general challenges faced in delivering and analyzing highly dependable service based systems. We quantify the challenges of dependability assessment utilizing a commercial case study. Furthermore, we explore one facet of dependability assessment related to log entries not necessarily related to dependability. We provide a novel approach to log filtering and show that the removal of benign log entries leads to more realistic system dependability analysis. We also show the need to merge multiple types of SaaS logs to support effective analysis.