All together now
The whole range
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 IBMs 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
In addition to creating a new user interface paradigm, the Web, or at least the Webs
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 months
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
- 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 Microsofts and Novells directory services whenever that
particular war has concluded.
The truth is that as the interface between the individual and the
host-based application has changed from dumb screen, through PC to client/sever, to
Web browser, all that has happened is that the mechanics of accessing legacy data has
evolved to keep in step. With the Windows NT server standing between the legacy host
application and the desktop, organisations have the opportunity to use the NT server to
manage access for an easier, simpler life.
John Stevenson was writing on behalf of Esker