CARRYON System Development

University of Siegen
Stefan Paal, Jens Wagner, Roger Sennert, Reiner Kammüller, Bernd Freisleben

15.08.2000

Abstract
The CARRY ON project is designed to be an internet installation, where different clients access a central database and the actions of a certain client (inspector) have to be propagated synchronously to other clients (browser) . Therefore, the system is not only an information system, but an interactive environment providing the users a virtual place with indirect communication. Many needed features for programming and running such an application are found in the CAT Network, thus CARRYON is built upon this architecture and represents a single component in the overall network installation of CAT.

System Requirements
For an internet installation it's essential to be accessible from most computer platforms, hence the implementation of CARRY ON mustn't rely on specific installation procedures, but rather on the built-in features of the popular internet browsers like Netscape Navigator or Microsoft Internet Explorer. On the other side, the client must use an active component for communicating with the server, displaying and manipulating the data. For this purpose, Java is selected, simply because it allows the platform independent implementation of the client part and is powerful enough for the intended tasks. In the current project, the rather outdated JDK 1.1.5 is used, since it's a built-in feature of the newer browsers and no extra installation is needed.

CAT Network The CAT Network is built upon a multi-tier-architecture with central adminstration and distributed extension over the internet. Among these runtime features it provides programming interfaces for seamless addressing of different database installation and types, transparent network communication and interaction with other components of CAT. Furthermore, the CAT Network represents a virtual community, where members not only can participate and communicate over the internet, but also extend it with own applications like CARRY ON. The core server area in St. Augustin is driven by the CAT Administration Team, providing database resources as well as computing machines, where extern application modules can be installed and published. Besides using this machines, one can integrate his own machine in the network and be part of the CAT Network. Thus, CAT offers several integration grades, suitable for various client needs.

CAT Integration
One example of tight integration in CAT Network is CARRY ON. Designed to be an internet installation, it requires network, database and computing support. But the artist doesn't want to reinvent the wheel, not to mention the waste of time, man power and money. Therefore, she decided to use the ready-for-use CAT platform, which provides the needed development and runtime support. Software engineers of the University of Siegen have taken over the implementation and administration of CARRY ON and installed the system on hardware of GMD. In the end, the artist could take care of her real art work, not having in mind, how to deal with the underlying technic.

System Architecture Due to its distributed character, CARRYON is divided in several parts which communicate via RMI and HTTP. Java Server There is one single CARRYON server located in the CAT Network. Its main task is the execution of client requests and coordination of the various client applets. It consists of two parts, the RMI Server and the Java Servlet. Each of it processes the requests from the applet respectively the browser and uses for these tasks the CAT Network Platform. Java Applet The active client component is built up with a Java Applet, which is used by the internet visitors to work with CARRYON. They are able to manipulate the data and look for modifications by others. For this purpose, the applet communicates with the RMI server and in turn, the server responds to all connected clients to synchronize their view on CARRYON. JSP Setup & Administration Before publication, the system and the database have to been set up with participant accounts and their data. This happens in special workshops (see CARRYON description of Shu Lea Cheang), where students provide suitcase images and upload them into database. This setup and the administration is done by a simple HTML interface, since there is no need for active processing on the client. However, conventional static web pages can't be used, because the HTML pages must display dynamic generated data from the server. For this purpose, the system uses Java Server Pages (JSP), which offers an easy way to create HTML pages on the server with Java, easily accessing the other parts of the system. In the end, the client receives only a pure HTML page, thus no special installation is needed.

Conclusion
First of all, we have briefly explained the goals, features and requirements of CARRY ON. Then we have described, the benefits of CAT Network and its open architecture for integrating extern applications and computers, resulting in adding CARRY ON as part of CAT. At the end, the system architecture of CARRY ON was shown in more detail.

CARRY ON is a typical example using the CAT Network for internet installations. An artist has an idea and looks for implementing her vision. But not qualified in software engineering nor having hardware equipment, she needs support for the technical issues, wherefore she contact CAT. With the aid of professional software engineers and the benefit of the available components of CAT Network the implementation time could be shortened without losing functionality.

Credits