Migrating Legacy Applications: Challenges in Service Oriented Architecture and Cloud Computing Environments

Over the past few years, we have witnessed a paradigm shift on the programming models and on architectural styles, which have been used to design and implement large-scale service-oriented systems. More specifically, the classic message-oriented and remote procedure call paradigm has gradually evolved to the resource-oriented architectural style, inspired by concepts pertinent to the World Wide Web. This shift has been primarily driven by multifaceted functional and non-functional requirements of Web enabled large-scale service offering systems. These requirements include enhanced interoperability, lightweight integration, scalability, enhanced performance, even looser coupling, and less dependence on shifting technology standards. As a consequence, several, and sometimes antagonistic, architectures, design patterns, and programming paradigms have emerged on a quest to overcome the constantly expanding enterprise software needs. In the context of resource-oriented architectures, the Representational State Transfer (REST) architectural style has gained considerable attention due to its simplicity, uniformity, and flexibility. More specifically, the potential for scalability and loose coupling, the uniformity of interfaces, and the efficient bridging of enterprise software systems with the Web are significant factors for software architects and engineers to consider REST when designing, implementing, composing, and deploying service-oriented systems. These issues stir discussion among academics and practitioners about how to properly apply REST constraints both with respect to the development of new enterprise systems and to the migration and adaptation of existing service-oriented systems to RESTful architectures. In this chapter, the authors discuss issues and challenges related to the adaptation of existing service-oriented systems to a RESTful architecture. First, they present the motivation