The importance of legacy systems is being undermined by the potential of web systems. This is a misconception as they run the mission-critical systems and deliver competitive advantage to many corporations.

Rather than looking down the nose at legacy systems we should treat them with the respect that they deserve.

The heritage of legacy systems

The Internet has totally changed the business environment. New environments accelerate evolution as the constituents adapt to survive. 

During 1998/1999 many corporations invested millions in making sure their business systems were capable of working after 31st December 1999. Why did they do it? They did it because these systems had embedded within them the business processes that ran their businesses. These systems are often described in a disparaging fashion as legacy; something we would rather not acknowledge exists and would like to throw on the rubbish heap. They should really be more positively described as the business heritage without which the business would collapse.

We are now in the year 2000. Internet is King. Portals are more than just doorways. The world is out there to be changed. All we need is a browser and a web server and we can become e-ised. With this mechanism we can extend the enterprise across the globe. Every person with an internet connection becomes a potential business partner. We have all read the same articles; we have been told many times how easy it is. So what is causing the problems?

Integration is the answer. You can build the worlds best user interface, you can have the worlds fastest web server but it still needs the data that is being controlled by those legacy systems, those applications that we want to forget exist. How do you get at it? We have to accept that these legacy systems are really the foundation upon which the e-business applications can be built, understand their worth and integrate with them.

There are two possible short-term ways to address this problem. One is to adapt the legacy systems to be web-enabled and the other is to treat the legacy systems as the back-office and use middleware techniques to integrate with the web-facing systems. This has spawned an industry supporting enterprise application integration (EAI), an interesting development that will further increase the sales of hardware to support the processing power that is required. The best way to address integration is via componentisation by treating the legacy systems as components within which the business-rules are encapsulated. This approach requires that the whole system is properly architected and not addressed in a spontaneous fashion.

The longer-term approach is to migrate to newer systems that have been designed from the ground-up for the web. This will mean reappraisal of the business processes (ubiquitous access to information), redesign of the supporting data (restructuring, reclassifying) and new, easy to use, user-facing interfaces. It will also be important that the new system is built using interchangeable, loosely coupled, components so that flexibility is maximised and maintenance is minimised.

It is interesting to note that the current web applications will become legacy within months as the technology evolves, leaving the current legacy, as the ultimate heritage, still running the major corporations.

All the business rules are still in the back-office legacy systems. The front-end web-based systems are for data capture and information presentation. These two worlds need to be integrated to ensure business benefits.