Maintaining and evolving Service Level Agreements: Motivation and case study

Inter-organization service-oriented compositions are governed by Service Level Agreements (SLAs). While the software is maintained and evolved in response to changing business requirements or technology, the governing SLA and software configuration designed to meet this SLA do not always change in step. SLAs are negotiated and may have legal standing, which makes their maintenance expensive and time consuming. If an SLA is established that meets the requirements of the service consumer, changing the software without updating the configuration and/or the SLA may result in unmet requirements and reduced satisfaction. This paper begins by examining the business perspective on SLAs as a guide and motivation to maintaining SLAs. A simulation-driven approach to updating a configuration in step with ongoing maintenance efforts is presented. The approach is illustrated using a case study, where we examine how a configuration is updated in two maintenance scenarios: one where the application is migrated to a cloud computing platform, and another where it is migrated to use a distributed computing platform. Our approach suggests configurations that maintain existing performance levels.