Software Modernization of Legacy Systems for Web Services Interoperability

IntroductIon Software maintenance is an inevitable process due to program evolution (Lehman & Belady, 1985). Adaptive maintenance (Schenidewind, 1987) is an activity used to adapt software to new environments or new requirements due to the evolving needs of new platforms, new operating systems, new software, and evolving business requirements. For example, companies have been adapting their legacy systems to Web-enabling environments of doing business that could not have been imagined even a decade ago (Khosrow-Pour & Herman, 2001; Werthner & Ricci, 2004). To understand software modernization of legacy systems for Web services, it is necessary to address how legacy integration has evolved from centralized computing to distributed, component-based computing due to the advent and widespread use of object-oriented and client-server technologies. Legacy systems were typically developed on a centralized, terminal-to-host architecture. Users usually accessed their legacy systems through terminals that included character-based menus and data entry screens. Consequently, legacy systems built on the central mainframe are inaccessible remotely without adaptations. Component-based middleware technologies , such as Java RMI, common object request broker architecture (CORBA), and component object model/distributed component object model (COM/DCOM), provide solutions to support the interoperability of legacy systems in a heterogeneous and distributed environment (Chiang, 2001). Unfortunately, the technologies have proved to be insufficient in application integration solutions for several reasons (Stal, 2002). Although the technologies share common communication architectural foundations, the implementation of each technology differs in several aspects, including the object models provided, the communication protocols, and data marshaling/demarshaling. Due to the proprietary implementations of the technologies, they do not interoperate well with Software Modernization of Legacy Systems for web Services interoperability each other. Obviously, existing component-based middleware only partially solves the interoper-ability problems of legacy systems. More effort is still required to make the legacy systems totally interoperable in a heterogeneous and distributed environment.