In the last decade, there have been significant developments in legacy to SOA evolution, and that has resulted in a large research body of which there exists no comprehensive overview. This chapter provides a historic overview, focusing on the methods and techniques used in legacy to SOA evolution. The authors conducted a systematic literature review to collect legacy to SOA evolution approaches reported from 2000 to August 2011. To this end, 121 primary studies were found and evaluated using an evaluation framework, which was developed from three evolution and modernization methods widely used in the software re-engineering domain. The evaluation constitutes the inventory of current research approaches and methods and techniques used in legacy to SOA evolution. The result of the SLR also identifies current research issues in legacy to SOA evolution and provides future research directions to address those research issues.
TopIntroduction
Recently, many enterprises have focused on increasing their business flexibility and achieving cross-enterprise collaboration to remain competitive in the market, and to meet their business objectives. Enterprises are especially challenged by constant changes in the business environment and changes in the supporting Information Technology (IT) infrastructures that hinder the overall success of enterprises (van Sinderen, 2008). Furthermore, most enterprises still rely on so called legacy system- software developed over the previous decades using 3GL programming languages like COBOL, RGP, PL/I, C, C++. Despite the well-known disadvantages, such as being inflexible and hard to maintain, legacy systems are still vitally important to the enterprises as they support complex core business processes; they cannot simply be removed as they implement and store critical business logic. Unsurprisingly, the knowledge contained in these systems is of high value to an enterprise. On the other hand, proper documentation, skilled manpower, and resources to evolve these legacy systems are scarce. Therefore, momentum is growing to evolve and reuse those legacy systems within new technological environments—Service-Oriented Architecture (SOA) being the most promising one (Bisbal, Lawless, Wu, & Grimson, 1999; Lewis, Morris, O'Brien, Smith, & Wrage, 2005).
SOA has emerged as an architectural style that enables the reuse of existing legacy assets within a new paradigm that facilitates loose coupling, abstraction of underlying logic, flexibility, reusability and discoverability (Papazoglou, 2008). The evolution from legacy to SOA can be beneficial from both economical and technical perspectives. From an economical perspective, legacy to SOA evolution fosters change management including intra-organizational changes, and changes in enterprises (Khadka, Sapkota, Pires, Sinderen, & Jansen, 2011; Papazoglou, Traverso, Dustdar, & Leymann, 2007). From a technical perspective, seamless enterprise collaboration through service composition (Khadka & Sapkota, 2010) and reduction in maintenance cost are claimed as long term benefits (Papazoglou, et al., 2007; Schelp & Aier, 2009). Motivated by these benefits, there has been significant research in legacy to SOA evolution. However, there is no systematic overview of legacy to SOA evolution, particularly focusing on the techniques, methods and approaches used to evolve legacy systems to a SOA environment. In the systematic literature review conducted by Razavian (Razavian & Lago, 2010), an overview of SOA migration families is reported. It focuses on classifying the SOA migration approaches into eight distinct families. The classification is inspired by the reengineering horseshoe method (Bergey, Smith, Weiderman, & Woods, 1999) rather than giving a historical overview of SOA migration methods. Also, a brief overview of legacy to SOA evolution is reported by Almonaies (Almonaies, Cordy, & Dean, 2010) that divides the legacy to SOA evolution approaches into four categories: replacement, redevelopment, wrapping and migration. The legacy to SOA evolution approaches reported in this research were not based on any systematic literature review process, so a complete, historical overview of the legacy to SOA evolution approaches is still lacking.
In this chapter, we provide a Systematic Literature Review (SLR) of the existing literature of legacy to SOA evolution. We provide a historical overview of the legacy to SOA evolution approaches reported in academia. We focus on identifying techniques, methods and approaches that are relevant to legacy to SOA evolution or that facilitate the legacy to SOA evolution process. In order to provide such a historical overview, we have developed an evaluation framework inspired by three software evolution frameworks reported in literature. The evaluation framework consists of six distinct phases and each phase has its own evaluation criteria to evaluate any legacy to SOA evolution approach reported in academia. The main contributions of this research are as following:
- 1.
A historical overview of legacy to SOA evolution.
- 2.
A legacy to SOA evolution process framework.
- 3.
An inventory of methods and techniques used in various phases of legacy to SOA evolution.
- 4.
A series of research issues and recommendations for future research directions.