Evolution Approaches Towards a Service Oriented Architecture Seridi Ali * Department of computer science, 8 May 1945 University LabSTIC Laboratory Guelma, Algeria a_seridi@yahoo.r Abstract- Over a decade, Service-oriented architectures (SOA) have seen an increasing interest of both academia and industry communities. This interest is associated with an enthusiasm of companies in different sectors and sizes for the adoption of this new paradigm due to its economic and technological beneits. SOA is a very effective response to the problems faced by companies in terms of reusability, interoperability and reduce coupling between systems that implement their information systems. To exploit these advantages many organizations have decided to evolve their legacy systems (LS) towards this architecture. Migration to SOA has become one of the most important modernizations technic of LS. It helps organizations, on the one hand, to reuse their existing LS by giving them a new life, and also to enj oy the beneits of service based systems. In the literature, several approaches exist for evolving LS towards SOA. Through this paper, we present a survey of these approaches. Then we discuss several existing classiications of the modernization approaches to SOA, so that at the end we propose our own classiication ater having discussed the similar works. Key-Words: Service Oriented Architecure; Evolution; Migration; Integration ; Legacy Syste. I. INTRODUCTION Service oriented architecture is an architectural style that supports service orientation [1]. It is essentially a collection of services that interact and communicate. This communication may be a simple retun of data or an activity (coordination of several services). The concept of service is better deined in business context than in a technical context. However, in an enterprise context, a service can be best described as a way to speciy encapsulated business unctionality independent rom concrete implementations. In this context, a service is more of a business concept than an IT concept [2]. The evolution of any sotware product over its lifetime is unavoidable, caused both by bugs to be ixed and by new requirements appearing in the later stages of the product's lifecycle. Traditional development and architecture paradigms have proven to be not suited for these continual changes, resulting in large maintenance costs [3]. If in the seventies, estimation studies claimed that maintenance consumed 67 % of total sotware costs [4], some Seriai Abdelhak-Djamel LIRMM/CNRS Laboratory, Montpellier2 University Montpellier, France abdeIhak. seriai@lirmm.r later authors talked about 90% [5]. Other studies have shown that approximately 50% of the time is spent understanding the code [6]. Solving bugs, improving performance, applying security patches or adding new features are part of the everyday jobs of a sotware developer. This has caused the rise of approaches such as Service Oriented Architectures based on loosely coupled, interoperable services, aiming to address these issues [3]. The problem is that most sotwares which are in operation worldwide are considered legacy, replace all of them would require exorbitant cost and effort. The tendency then is to evolve these systems towards more agile lexible architectures and less costly in maintenance, in our case the SOA. In this paper, we focus on the study of different approaches to modenize legacy systems (LS) towards service-oriented architectures (SOA). Modenization of LS can be done in several ways, among them, the redevelopment which is a complete rewrite of the system rom scratch in a new technology; integration consists on keeping the old system without modiying the source code while adding a new sotware layer (wrapping) to extenalize its unctionality and interact with the new service-oriented system when migration, aims to resructure and ransform a LS into a more lexible while keeping the original data and unctionality. The rest of this paper is structured as follows. The next section inroduces the notion of LS. Section 3 surveys various legacy integration and ransformation approaches and reviews some representative example while section 4 presents discussion of related work. Section 5 details our proposed classiication. Section 6 presents some criteria which extend existing criteria used to compare several approaches and Section 7 concludes the paper and provides some directions for uture work. II. LEGACY SOFTWARE Legacy Sotwares are programs that have been developed with technologies that have become outdated. Brodie & Stonbraker in [7] deine the legacy infonnation systems as "Any system that signiicantly resists modiication and evolution". Legacy sotware includes now not only the early languages of the 1970's - Fortran, COBOL, PLI ,C - but also 978-1-4673-1520-3/12/$31.00 ©2012 IEEE