WWW/Internet - Portal do Software Público Brasileiro

IADIS International Conference WWW/Internet 2010for low-end PCs. However, the Aspire Revo is sufficient to browse the Web and process mail. Therefore, it iscalled a ”Nettop” computer. Browsing the web is the one and only one task for each Player. For that reason,we chose Nettop computers as WDiMs Players.Coordinator is a middle range computer. The specifications for the Coordinator are the following: CPU,Core2Duo T9300 (Intel Corp.); Memory, 2 GB; HDD, 250 GB/ 5400 rpm.Generally speaking, tiled display walls such as WDiM are bottlenecked by the performance of theCoordinator computer because Coordinator must orchestrate all Players. Although network traffic and theload average are directly related to the number of Players and LCD panels, they do not present an importantproblem because the WDiM system described herein has only 16 LCD panels. In addition, much knowledgeand technology of load balancing exists, e.g., web server clustering, web proxy, and so on. The measurementof scalability remains as a subject for future work.The four vertical LCD panels and four Player PCs are installed to the same aluminum frames with VESALCD monitor arms. Each frame has casters; thereby, WDiM is movable.As explained herein, WDiM consists of low-cost electronics. We spent less than fifteen thousand dollarsto build WDiM, although it has more than 16 LCDs tiled on a display wall.2.3 NetworkAll of the Coordinator, Player, Conductor, and a gateway components connect to the network, whichsupports Gigabit Ethernet; the WDiM is connected to the internet via the gateway. Therefore, internal devicesof the WDiM cannot access only the external web services; external devices can also access to the internaldevices of the WDiM. In other words, an iPhone and laptop computer can control a web application on theWDiM.In actuality, WDiM, which is based only on web technology, uses no network protocol except HTTP,which is an application-layer protocol. Consequently, Players cannot send and receive data to each other andthe Coordinator cannot call Players. The web browsers from (Players and the Conductor) send requests tothe web server (Coordinator) and receive responses. This is an HTTP specification.Consequently, all Players and the Conductor poll the web server on the Coordinator using Ajax behindweb application on WDiM. The flow described above is hidden from WDiM application developers becauseWDiM middle-ware provides an overlay network and its access methods over the troublesome HTTP/Ajaxmessaging (Figure 3).3. WEB, COMPOSABLE WEB, AND DECOMPOSABLE WEBOnce it was believed that web browsers were useful merely to display static pages that web servers wouldprovide one after another. However, web pages are no longer static; a good example is Google Maps, whichFigure 3. WDiM messagingFigure 4. Model-View-Controller (MVC) of WDiM153