Apr 21 ’10

Legacy Modernization:  SOAring Legacy

by Len Erlikh 

Evolution of corporate IT systems beyond the boundaries of the traditional enterprise and the dynamic nature of the competitive landscape are creating significant business and technology challenges. These challenges present themselves in the very scale and reach of the newly created applications and the speed with which the new business models are being introduced into the extended enterprise. Modern enterprise architectures require a radically different technological approach to building and connecting applications into coherent, large-scale solutions. This dynamic business scenario renders obsolete the traditional notion of coordinated, enterprisewide architectures and introduces a more agile paradigm of loosely coupled SOA and Web services-based solutions. 

Service-Oriented Architecture (SOA) and Web services are the leading industrywide initiatives focused on addressing the need for connecting these extended enterprise applications into cohesive business models. SOA and Web services initiatives are mature and time-proven technologies that have evolved over the last 10 years. 

Over the years, we’ve experienced the evolution of ever more sophisticated application integration technologies focused on reducing the coupling between participating system components. The emergence of asynchronous, message-based communications, relaxation of the rigid information exchange requirements supported by self-defining data formats, and the negotiated distributed transactional models are some of the key technologies that laid the foundation for loosely coupled architectures. SOA and Web services build upon these pre-cursor technologies to deliver the next generation of application integration solutions. 

SOA Key Principles

SOA architecture packages business functionality as interoperable services within the context of the various business domains involved. Multiple business entities (internal or external to the enterprise) can integrate or reuse such services—software modules provided as a service—even if their respective client systems are substantially different. SOA defines the interface in terms of protocols and functionality. SOA requires loose coupling with all layers of the technology stack—starting with the underlying operating system and ending with collaborating applications. 

The key principles of SOA are: 

SOA and Legacy Systems 

Given that legacy systems are still at the heart of modern-day IT application portfolios, there’s a strong corporate desire to integrate these legacy systems into enterprisewide SOA architectures. No extended enterprise solution is complete without a viable approach to embracing the legacy platform into its composite applications. The great promise of SOA and Web services is in their ability to flexibly and efficiently connect a diverse set of technologies, including legacy systems, into the extended enterprise framework. 

SOA and Web services place several very specific architectural requirements on the way the underlying business function needs to be implemented. It’s clear that legacy systems fail to address these architectural requirements. Legacy systems are monolithic in their very nature, as they were originally designed and developed for the single, homogenous platform. These systems were built using rigid, hard-wired business process flows with no notion of composite event definition. It’s clear it isn’t possible to properly integrate legacy systems into SOA-based solution frameworks without major, intrusive modifications to these systems. These modifications need to reshape legacy systems to provide a natural fit with the SOA and Web services architectural requirements. The complexity and magnitude of this task can’t be managed without a considerable degree of technological innovation and automation. This is equally true for both the enterprises’ private and public business processes. 


The prominent role legacy systems maintain in the corporate IT portfolio makes it imperative for extended enterprise solutions to provide a viable strategy for integrating these systems into SOA frameworks. Significant invasive modifications of legacy systems are needed to turn them into componentized structures that have a natural fit with SOA and Web services. Advanced legacy modernization technologies make this type of legacy modification possible.