Introduction

Before delving into this analysis, it is important to ensure a common understanding of the key terms used here. Wikipedia defines a legacy system as an existing computer system or application program that continues to be used because the user (typically an organization) does not want to replace or redesign it.

This definition is fairly broad—applying to a number of different computer systems. It can also refer to a system that is out of date or difficult to replace, due to the high cost or risk associated with doing so. For the better part of the last 40 years, enterprises have chosen to host their most mission-critical applications on the most thoroughly proven legacy computing environment available, the mainframe. This analysis will focus on legacy mainframe computing.

Service-Oriented Architecture (SOA) is a software architectural concept that defines the use of services to support the requirements of software users. In an SOA environment, network nodes make resources available to other network participants as independent services, which participants can access in a standardized way through well-defined service interfaces. It functions both as a software development and a delivery framework.2 The focus of this analysis will be on SOA’s ability to provide a mechanism for defining business services and operating models. Doing this successfully provides a technological infrastructure that an IT organization can use to both adapt to the business needs of an organization, and also deliver against actual business requirements.