About ICONSnet

Following is a technical overview of ICONSnet, ICONS’ simulation support software. For information on using ICONSnet, please see the ICONSnet User Guide. For a more complete discussion of the ICONSnet development process, please see "Maintaining Pedagogy while Changing Technology."   (A later version is available in PDF format.) To try our Demo Community, please go to http://www.icons.umd.edu/demo.html and register.

Background
ICONSnet is the replacement for POLNET II^*, which ICONS had used to run simulations since the mid-1980s.  By 1995, the World Wide Web and related technologies made it possible for ICONS to provide users with an easy-to-use interface, coupled with accessibility from any computer with an Internet connection and a web browser. After examining and testing some commercial packages, ICONS developed an entirely new software package, ICONSnet, that replicated and enhanced the essential features of POLNET II in a web-based database application.  (See ICONSnet Features for more information.)

Development
ICONS decided to build a customized system based upon a commercial relational database program. We chose Oracle because of its reliability in handling large databases, and because at the time we were deciding among alternatives, Oracle was the only company to offer a web server application that connected directly with the database. Since time was of the essence and resources were limited, priority was given to the ability to develop a user interface that ran on the server side without having to build the software to connect from a web application to the database.

Oracle Web Application server makes the connection between a web based application and the database transparent. An Oracle cartridge uses the HTTP communication protocol and is a shared library that either implements or accesses application logic stored in an Oracle database. ICONSnet is built upon the PL/SQL and Jweb web cartridges. The application logic is written in Oracle’s proprietary language PL/SQL, which allows the addition of complexity to standard ANSI SQL statements with the packages stored directly in the database.

ICONSnet is written as a series of PL/SQL packages. It was developed during Fall 1996 and Spring 1997, pilot tested in Spring and Summer 1997, and fully implemented in Fall 1997. It underwent a major revision in 1998. (In addition, we make regular modifications to respond to user input and to upgrade to new versions of Oracle tools. For example, a Proposal Center was added to ICONSnet in March 2001.) When using the ICONSnet system, participants input data into a series of customized forms, which allows them to submit data to the database (e.g., sending messages either asynchronously or in a conference) or request data from the database (e.g., reading new messages, reading conference messages, or accessing the archives).

Most of the pages the participants access contain dynamic data, except for the login page. Each button calls a PL/SQL procedure that customizes the information shown on the screen. For example, in an international simulation, Canada and Mexico may see different information on the screen. Messages that are sent to all participants will be seen by both, but Mexico will not be able to access messages sent only to Canada.

Servers
ICONS maintains three Windows NT 4.0 servers, two running Oracle Application Server 4 and one running Oracle Database 8. The database server, donated to ICONS by NCR Government Systems, has 4 Pentium processors and 512 megs RAM. The application servers each have 2 Pentium processors. The primary server has 1024 megs RAM, and the backup server has 256 megs RAM.

^*POLNET II is a file-based program, written in C and run on a UNIX platform.

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Last modified: April 4, 2001