There was a time when integrating legacy applications and data with a modern desktop was a black art, a task suitable only for those with the appropriate cloak and wand. Today, there is a plethora of products on the market that purport to help you integrate Windows NT with legacy systems, applications and databases on Unix, AS/400 and mainframe systems.

All together now

In the days of basic peer-to-peer networking, the most viable approach was to provide integration between the legacy system and the desktop PC using a terminal emulation. As long as it was possible to load an IP stack on the PC, it was possible to deliver a basic green screen terminal emulation session onto the PC desktop.

A further refinement came with the introduction of Microsoft-developed standards for accessing data on host databases. The ODBC standard made it possible to call host-based databases from Microsoft and Windows desktop products, select data according to a set of criteria and return the results into the calling application. With this approach you could also get data from an Oracle database running on IBM’s AIX Unix into a Microsoft Word mail merge. You could also use the same approach to extract data from an AS/400-based billing system and use it in a Visual Basic application and thus develop client/server applications.

In addition to creating a new user interface paradigm, the Web, or at least the Web’s associated technologies (IP, HTML, Java, ActiveX), has created a new mechanism for integrating Windows NT with legacy applications and data. Rather than simply taking an emulation and running it in a self-contained window on a PC (or taking a data stream from a legacy database and squirting it into certain fields in Word or Excel), it is now possible to design and develop Web applications that call data from legacy applications. More importantly, it is possible to do this without the user ever being aware of the presence of the legacy application running in the background.

The whole range

Good legacy integration products will allow a tolerably proficient IT professional to deliver legacy applications and data direct to the desktop, using NT as a communications server between the source data and the desktop. The better ones will allow you to access the full gamut of source legacy databases including Informix, Oracle, Ingres, Progress, C-ISAM files and DB2. They will offer you the option to run terminal emulation sessions or access data streams. They will also let you deliver the application data in the most appropriate method – plain old emulation, re-vamped emulation (see last month’s Jargon Buster), data stream captured using ODBC or into your web browser.

Most important of all, a good legacy integration product will let you use the power of the Windows NT server to manage access between the desktop and the legacy application. Here are some points to consider:

• Centralised deployment: A good integration product will allow you to deploy access to large numbers of PC desktops from the NT server without having to ‘touch’ each individual desktop. For example, such products will allow you to define individuals and groups of users and specify the types of access they need (e.g. access to certain host applications). You can then deploy centrally, saving valuable time and money.

• Centralised management: Look for a product that offers centralised management of the PC population. Also look for products that provide tight integration with Windows NT system management tools.

• Directory services: Directory services offer a rapid and effective way of identifying and accessing every individual and resource on the network. This makes the directory service the perfect place to store details about users/groups of users and their host access requirements. Directory services are still emerging (with both Novell and Microsoft promising to rule roost). So look for products that offer directory services centred around proven standards (like the Internet LDAP standard) as well as promising support for both Microsoft’s and Novell’s directory services whenever that particular war has concluded.