This chapter presents the fundamental ideas related to migrating legacy applications to service-oriented systems, and provides an overview of the available approaches that are presented in this book. The goal is to provide a “big picture” while also analyzing each chapter and indicating the way it covers several essential concerns, such as state-of-the-art, methods, standards, tools, business perspective, practical experiments, strategies, and roadmaps.
TopIntroduction
Nowadays, the business landscape is profoundly influenced by changing ownership paradigms. On one hand, the complexity of software applications has continuously increased mainly due to incorporation of advanced technologies; this phenomenon has critically required a “divide et impera” approach, leading to a wide distribution of resources, activities, artifacts, and projects. This distribution can be seen from several points of view:
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Technical: With the rise of the distributed processing era in 1990 (Greenfield, 2004);
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Managerial: With the proliferation of multi-partner projects, or by outsourcing part of product development and services to third-parties;
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Geographical: Working with and for people worldwide, and relocating certain activities of business processes.
The degree of globalization continues to increase and has gone through three important stages (O’Brian, 2008):
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International: With foreign subsidiaries based on local information systems;
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Global: Including worldwide operations;
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Transnational: With central information systems supported by the Internet.
One can see that, apart from decomposing—sustained by the first part of the Latin maxim “divide”—there is an increasing need of the second part: “impera.” This is expressed as new approaches and trends for sharing resources, connecting people, offering support for collaborative work, or managing software artifacts.
In this context, ownership is also much more distributed than before, requiring better specification of agreements between partners; interoperability support represents a priority for technical stakeholders. One way of dealing with these challenges is a shift towards service provisioning, based on advanced Information Technology (IT) infrastructures, platforms and software, as well as on a holistic approach that involves specialists from economy, engineering, social sciences, and arts (Donofrio, 2010). This trend is also influenced by an increase in the workforce in the service sector, which is valid for countries with various levels of development (Sporer, 2007).
However, enterprises are not in a hurry to give up to their legacy and abruptly switch to service-oriented systems. The main reason is economic because business processes cannot be suddenly modified and introduction of new technology has its costs. Therefore, it is more and more clear that the transition towards completely new systems is rarely an option. Except for startups, it becomes vital for enterprises to reuse their legacy systems as application front-ends and back-ends. It is also important to do it in a gradual manner. Indeed, there are quick solutions for moving applications to run on Cloud infrastructures (Varia, 2010), but this is only possible under certain conditions: statelessness and decoupling from external agents. It is difficult to conform to the latter and, at the same time, stay aligned with current trends. Generally, the move towards service provisioning requires supplementary work for wrapping or completely reengineering existent code; buying new services, platforms or infrastructures; reanalyzing business requirements; and conducting a forward-engineering process with the constraint of reusing as much as possible.