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Screen
mapping is a technique by which data are moved in and out
of a host system via the terminal interface. A common gateway
interface (CGI) links the screen mapping application to
the web server. Since the screen mapping program looks just
like another user of the host system, applications can be
easily built without the need to modify or have access to
the host system code. Screen mapping is particularly well
suited to web enabling existing enterprise systems. It has
been used successfully to expand access to enterprise information
via the web as well as provide the facility to integrate
on-line order processing with enterprise fulfillment systems.
Existing tools can be plugged into the CGI to handle encrypted
browser connections, credit card transactions, or save sensitive
customer information.
It is important to note that screen mapping techniques of
today have progressed from the "row and column" coordinate
screen scraping systems of the past. Today's screen mapping
has evolved into a more robust "pattern-based" system. The
use of patterns easily allows for complex interaction with
the host, and reliance on patterns virtually eliminates
application maintenance as minor modifications are made
to the host system screen. Another departure of from screen
scraping is the ability for screen mapping to interact with
multiple systems simultaneously thereby allowing data from
multiple sources to be combined to form a new presentation
interface. Again, using screen mapping, all of this can
typically be done without modifying the host system. This
is futher augmented by the ability to use different screen
protocols for each system from which data is collected.
In this way, data from multiple vendors can be cross referenced
with each other to create information from the data, or
can be displayed as a single web page rather than multiple
text screen dumps.
The
primary advantage of this technique is the speed at which
applications can be deployed. A graphical configuration
tool gives the developer a virtual green screen showing
them the application fields. It is then a simple case to
drag each field that is required to a template of variable
names. The variable names can be renamed to useful names
that the webmaster will know. The webmaster can then take
the defined variables and insert them into the corporate
web pages so that the host system data is seamless with
the already existing site. Development times for applications
are measured in days. This is due to the fact that all interaction
with the system is done through the screen interface. This
eliminates the need to write code to directly access the
many various databases that may contain the enterprise data.
Since the entire interface is text based, it provides an
easy to debug development environment.
There
are some things to consider before using screen mapping
techniques. First, block data terminal types such as 3270
and 5250 are usually better suited than VT100 serial terminal
types. Some screen mapping development environments do support
serial data handling, but it is a more difficult environment
in which to work. Also, if major changes to the host system
are made on a regular basis such as moving data to different
screens this will normally force reconfiguration of the
screen mapping application. Screen mapping is best used
on mature applications running on mainframe or mid-range
systems.
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