Abstract. Cloud computing has leveraged new software development and provisioning approaches by changing the way computing, storage and networking resources are purchased and consumed. The variety of cloud offerings on both technical and business level has considerably advanced the development process and established new business models and value chains for applications and services. However, the modernization and cloudification of legacy software so as to be offered as a service still encounters many challenges. In this work, we present a complete methodology and a methodology instantiation framework for the effective migration of legacy software to modern cloud environments. 1. Introduction. Nowadays, cloud computing [4] appears as one of the most popular and mature technological and business environments for engineering, hosting and provisioning software applications. A continuously increasing set of cloud-based solutions across the cloud stack layers [11] is available to application owners and developers to tailor their applications and exploit the advanced features of this paradigm for elasticity, high availability and performance. These solutions provide many benefits to new applications but they also introduce constrains to the modernization and migration of legacy applications. We consider legacy applications as software not developed for the Cloud and software in traditional architectural paradigms that cannot be scaled, cannot be measured and does not share resources beyond infrastructure (e.g. database, memory). Often the legacy applications follow monolithic architecture design approaches, implemented in technologies which may be deprecated or cannot easily deal with the notion of "as a Service" and are installed on owned infrastructures.The modernization and adaptation of legacy applications to cloud environments is a great challenge for all involved stakeholders, not only from a technical perspective, but also in business level with the need for adaptation of the business processes and models of the application which will be deployed on the Cloud and offered "as a service". In this paper, we present a novel model-driven [22] approach for the migration of legacy applications in modern cloud environments which covers all aspects and phases of the migration process, as well as an integrated framework that supports all migration process.Our motivation for this work is the requirements and challenges for the effective migration of legacy software on the Cloud as described in [9]. To this end, the proposed migration methodology considers the following aspects:• Unknown internal structure due to the complexity of the software and the data management processes.• Lack of knowledge for target environment where the application will be deployed and provisioned.

Nowadays Cloud Computing is considered as the ideal environment for engineering, hosting and provisioning applications. A continuously increasing set of cloud-based solutions is available to application owners and developers to tailor their applications exploiting the advanced features of this paradigm for elasticity, high availability and performance. Even though these offerings provide many benefits to new applications, they often incorporate constrains to the modernization and migration of legacy applications by obliging the use of specific development technologies and explicit architectural design approaches. The modernization and adaptation of legacy applications to cloud environments is a great challenge for all involved stakeholders, not only from the technical perspective, but also in business level with the need to adapt the business processes and models of the modernized application that will be offered from now on, as a service. In this paper we present a novel model-driven approach for the migration of legacy applications in modern cloud environments which covers all aspects and phases of the migration process, as well as an integrated framework that supports all migration process.

The authors discuss important factors to consider when migrating software to the cloud and offer recommendations to maximize the chance of success. Organizations undertake more and more software modernization projects every day, mostly owing to rapid changes in the technological landscape pushing them to evolve their systems before those systems become obsolete. Such projects are sometimes taken too lightly and start more because of passing fads than because they're motivated by real technological limitations or system problems. In our experience, many managers have only a partial view of these projects' complexity and consequences.A modernization project usually has three phases. First, reverse engineering provides an understanding of the system's purpose and current state. Many supporting approaches rely on model-based techniques to discover software models representing the system at a higher abstraction level. Examples of such models are UML (Unified Modeling Language) class diagrams, state machines, and workflows. Second, forward engineering analyzes those models and transforms them (if Selected CS articles and columns are also available for free at http://ComputingNow.computer.org.

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