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The Web, Legacy Architectures, and The Fourth Wave
by William Ulrich
Companies are seeking ways to integrate the Web with legacy data and application functionality. Having built or rebuilt Web sites to
address customer, supplier, or distributor requirements, companies are seeking to enrich Web-based applications with business
functionality ranging from order handling to procurement. The functionality they need, however, is embedded in legacy systems.
The solution to this challenge comes in waves-based technological advancements and our growing understanding of what we are trying to
accomplish.
The Web has opened up new opportunities to businesses wishing to streamline relationships with customers, distributors, business
partners, and suppliers. To make these opportunities a reality, however, critical enterprise data and legacy systems functionality
needs to be Web-enabled.
Because legacy systems are the gateway to enterprise data, these systems have become targets of a series of recent IT initiatives.
These initiatives can be broken into four waves that bring together enterprise data, legacy functionality, and
Web-based environments.
* 1st wave: Build and deploy new Web sites.
* 2nd wave: Integrate Web-based front-ends with legacy systems using middleware technology.
* 3rd wave: Web-enable legacy systems using semi-invasive technology.
* 4th wave: Extract, transform, and reuse legacy data and business logic under newly defined strategic architectures.
The first wave is mostly in place, although organizations will be retooling Web sites for an indefinite period of time. The second
wave has been under way for the past several years. Middleware is an accepted form of linking Web-based front-ends to legacy
applications. For example, a customer or business user may place an order through a Web site that triggers a back-end CICS transaction
that actually places the order. To the customer or user, it looks like this was done by a Web-based system as opposed to an old legacy
system.
While this is a nice first step, the entire customer business process including order confirmation, inventory maintenance, procurement
functions, billing, and shipping cannot be triggered through a single legacy transaction. It would be nice to make all of this work
seamlessly, but legacy systems do not work this way because much of the processing in a legacy environment is done at night during batch
processing cycles through a series of stovepipe systems.
A slightly better approach is to Web-enable the legacy application using tools that make the legacy system interface with the Web-based
front-end directly. Tools allow IT to migrate green screens to Web-based front-ends and update legacy
programs to access these screens. While this is a better approach than that applied by older
middleware applications, legacy architectures remain a series of stovepipe transactions that rarely accommodate Web-based requirements.
The second and third waves create hybrid or "composite" systems made up of old technology and new technology. Composite systems will
always have clashing architectures that IT will find onerous to enhance and manage. More important, composite systems rarely fulfill
the business requirements idealized in the first place.
In the future, IT teams will need to define a new Web-driven architecture, under J2EE or .Net for example, and migrate data and
business rules into this new environment. This fourth wave of legacy-to-Web integration requires vision, careful planning, phased
deployment, and patience. In the meantime, IT will need to deploy systems under the second and third wave while keeping a close eye on long-term information architecture requirements.
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