XML Application on a Unix Server

This article explains how we used XML and XSL to allow our users to run applications viewed in HTML, from a Unix server.  This architechure is very similar to a SOAP implementation, except that we used our own message calls between the front end and the server.

The architechure's backend used an Informix database stored on a Unix server.

Originally we developed a client-server application running on Unix.  Each user runs the Unix applications via our Unix terminal emulation on their PC.

We then decided to move over to an intranet applications based on the ASP technology. Due to Unix not supporting ASP, we programmed our own modules and the application servers (cgi programs running on Unix).

Each user runs the applications from his PC by calling the URL address of the ASP pages (these pages were saved on the Unix server).

We developed the intranet applications, which communicates with the XML application servers, which are scgi programs running on the Unix system.

Before I continue, the following diagram outlines the architechure we used:

The application's principle

• HTML
• xsl
• css
• js
• scgi programs (the so called "XML application servers")
• informix database

Web server on the Unix server

This page is displayed with a form binding to some XML data.  The user chooses one of the actions from the menu of the displayed HTML.

The javascript function that generates the "communication XML structure" (the so-called "XMLforsever") is executed .  The instance of XMLHTTP object is created. This object sends "XMLforserver" to receiver - XML application server - via the web server.

The XML application server (scgi program running on the Unix) gets structure "XMLforserver" to its standard input, handles it via the classes for the work with XML, and stores "XMLforserver" structure to own objects.

The content of "XMLforserver" says to the XML application server which operation to execute, which parameters to use.

XML application server executes specified operation (the format of output for each operation has XML application server encoded inside) and generates new XML communication structure("XMLforclient"). This structure contents result type of operation, retrieved data and message for user .

The structure "XMLforclient" goes back to the HTML page via XMLHTTP object again.  Then the javascript function analyses content of retrieved structure (via XMLDOM objects) and runs corresponding xsl transformations to display result of action chosen by user.

Example code

Communication with xml application server Input data: ("xmlforserver")

For each operation on the server – the xml structure from the client:

Structure:

For each operation tags OPERATION and DATA have another content

For each operation on the server – server generate xml structure for client:

Structure: