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Why Deploy on the
Web?
Deploying your 4GL applications
on the Web offers the following benefits:
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No need for special
programming
You can deploy your existing 4GL applications on the Internet or an Intranet. |
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Preserve application
appearance and functionality
You can run your Dynamic
4GL application on the Web as easily as you can run it on your local machine. |
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Ability to configure
the user interface
You can customize your application's user interface to optimize it for display
on the Web. |
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Consistent application
and database development
You can create applications for deployment in different environments using
only one tool; you can reuse your existing application logic; you can use
the same database for all of the environments in which you deploy your application. |
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Security
You can take advantage
of options like firewalls and SSL (secure socket layer) in addition to preserving
the security features in your original application. |
Limitations
Some limitations appear due to Web
technology. With your ASCII 4GL, each character is analyzed as it is typed.
With local editing in Dynamic 4GL, each field is analyzed on the display
server and transmitted to the runner when the field is completed. With Dynamic
4GL applications deployed on the Web, each page is transmitted to the server,
which has the following effects:
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Only the top-level window
is visible and it appears as one HTML page. Popping up a sub-window therefore
creates a new page, and only the information displayed on the sub-window
is visible to the user. |
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The ON KEY actions do not work during input statements
because the Dynamic 4GL program does not see the individual keystrokes.
For the same reason, the COMMAND KEY options in menus also do not work. |
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The BEFORE FIELD and AFTER FIELD clauses
have no effect on the input sequence. The Dynamic 4GL program receives all
data after it has been entered. This also means that NEXT FIELD has no effect, and that displaying the
results of lookup data has no effect, either. You can use the BEFORE FIELD and AFTER FIELD clauses
to validate the entered data, but there are limits on what you can do when
the data is incorrect. |
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The SLEEP statement without interaction has no effect. |
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The PROMPT statement has no effect. |
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The DISPLAY ,
MESSAGE , and ERROR statements only take effect when the user
interacts with the program, such as when an INPUT,
INPUT ARRAY, DISPLAY
ARRAY, CONSTRUCT, or MENU statement is used. |
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RUN
WITHOUT WAITING can be
used, but it cannot be used to start a new Dynamic 4GL program which interacts
with the user via the web browser. The user must decide to access the new
program. |
Enhancements
There are additional enhancements
that you can add to your applications:
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Customized page headers
and footers |
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HTML tags in the screen
portion of the form |
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HTML tags as labels |
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HTML tags in your 4GL
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These enhancements are described
in Deploying a Sample Application.
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