6.Technology The system consists of Client-tier, Middle-tier, Database and Presentation-tier. Client devices such as cell phones and Palm Pilot interact with a Flash application through the middle-tier applications and database system. Figure 1.Guerrilloffiti System Diagram 1) Client-tier Any Internet-enabled devices equipped with HTTP or WAP browser (WML1.1 or HDML2.0+compliant) can be used to send messages to the board. (For a full list of supported devices and browsers, see Appendix B. List of supported devices) Since most of the handheld devices are limited in their resources, the user interface for these devices are optimized for a simple submit form and a confirm message. 2) Middle-tier This tier consists of a Java servlet and other Java applications running on a Java Application Server. Message Dispatcher Servlet first detects client device types and returns appropriate files for the particular device. When it receives a message from a client, then it interacts with other applications in order to relay and store the message.   Message Relaying Server handles socket connections   to the presentation-tier and relays messages from   the servlet to the presentation.   Database Handler interacts with SQL database system   to store and retrieve messages upon requests.   Timer checks the status of system regularly at a   certain interval. If the system has been idle for   a certain amount of time, it triggers a mechanism   to replay the old messages stored in the database   on the presentation.   Device Property File holds device and browser information   such as device type, manufacturer and accepted MIME   types for each device supported by the system.   This file is used by the servlet to detect client   device types. 3) Database A SQL relational database system stores messages from users. And optionally, the database can be configured to hold user information such as device and browser type, IP address and access time so as to keep track of users participations. 4) Presentation-tier This is a Macromedia Flash application that runs either on any traditional web browsers with Flash player plug-in, or as a standalone application. It connects to the Message Relaying Server via TCP/IP and draws messages on a display device in a particular way. Figure 2.Guerrilloffiti System Architecture | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | Appendix | A1 | A2 | A3 | A4 | A5 | A6 | B0 |