Leveraging Host Applications
The benefits of a host integration solution
Why might you consider a host integration solution?
- A host integration solution exposes host functionality as XML services to heterogeneous client applications built on technologies such as J2EE and .NET.
- A host application need not be changed to expose its functionality as services.
- A host integration solution can be deployed in a short timeframe.
- A host integration solution provides a layered architecture and acts as an adapter to the host application.
- A new user interface, unconstrained by the host application, can be built, but still leverage the host application as the system of record.
The consequences of a host integration solution
Let's look at the consequences of choosing host integration products:
- Data capture rules and edits present in the host application will need to be duplicated in the client applications. This will cause duplicate maintenance. If the edits are not kept in sync, a service request may fail when the host integration software is performing the requested function in the host application.
- As with web-to-host solutions, a host integration solution usually will require changes to services when the host screens change.
- As with web-to-host solutions, the functionality of the service will be limited to the functionality of the host applications being accessed.
Host integration vendor products
Leveraging Host Application Considerations
There two sides of a coin that you should consider when thinking about leveraging host applications through web-to-host or host integration products.
First side of the coin
A host application may be thought of as a company asset that has paid dividends over and over again. You could view the host application as money in the bank. Leveraging the application means earning interest.
Second side of the coin
A host application may be thought of as a huge liability that is costly to maintain, inflexible to change, and a competitive disadvantage. You could view the host application as a ball and chain holding you back. If it is money in the bank, maybe it's in a very low-paying CD losing ground to inflation.
Which of these views is correct? It is hard to say. In some sense the host application is an asset. However, there is a point when an asset becomes a liability.
There is no denying that web-to-host and host integration products provide the ability to leverage existing assets. Host applications can be quickly exposed as HTML user interfaces or XML services. But in either scenario, limitations of the host application live on and duplicate maintenance becomes necessary.
Re-writing a host application can be a daunting task. There is a great deal of business logic to be harvested from the host application. The host application may have a very high bar in terms of functionality that needs to be delivered even in a first release making replacement difficult in a short timeframe.
Web-to-host and host integration products could be used in a transition strategy. Consider the following scenarios:
- An HTML user interface could be provided through web-to-host software while pieces of the application are re-written in newer technology.
- Services could be built with host integration products to maintain the host application back-end functionality while creating a new user interface. This strategy would allow the presentation tier and resource tier upgrades to proceed independently or in parallel.
These and other incremental approaches could be more practical than a big bang approach. In terms of our banking analogy, we would be putting the money from the low-paying CD into better-paying investments gradually over time rather than in one fell swoop.
You could say that the trouble with many host applications is that they work. As much as we want to replace them, we need to manage these existing assets and co-exist with them.
Web-to-host products provide an HTML user interface to host applications. Host integration products expose host functionality as XML services. These tools can be used to extend the life of these assets and to expose them in new ways. Both classes of products do not require changes to the host application itself. While they require duplicate maintenance and maintain the limitations of the host application, they can be a part of a transition strategy to eventually retire these applications.
Are your host applications assets to be leveraged or liabilities to retire? Will you webify, servicize, rewrite, or simply live with your host applications? The rest is up to you!
1 Gartner, Noninvasive Legacy Web Enablement Is Still Viable, March 2003
2 Gartner, Programmatic Integration Servers Are a Growth Opportunity, March 2003
About the Author
|Jeff Ryan is an architect for Hartford Financial Services. He has twenty years experience designing, developing and delivering automated solutions to business problems. His current focus is on Java, XML and Service Oriented Architecture. He may be reached at firstname.lastname@example.org.|
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