Software Engineering Institute

Information systems are critical assets for modern enterprises and incorporate key knowledge acquired over the life of an organization. Although these systems must be updated continuously to reflect evolving business practices, repeated modification has a cumulative effect on system complexity, and the rapid evolution of technology quickly renders existing technologies obsolete. Eventually, the existing information systems become too fragile to modify and too important to discard. However, organizations must consider modernizing these legacy systems to remain viable. The commercial market provides a variety of solutions to this increasingly common problem of legacy system modernization. However, understanding the strengths and weaknesses of each modernization technique is paramount to select the correct solution and the overall success of a modernization effort. This paper provides a survey of modernization techniques including screen scraping, database gateway, XML integration, database replication, CGI integration, object-oriented wrapping, and "componentization" of legacy systems. This general overview enables engineers performing legacy system modernization to preselect a subset of applicable modernization techniques for further evaluation.